[Manabi]

If you're an Amazon Prime member you have free access to a couple of series of short stories/novellas written by well known science fiction authors. You don't get permanent access to them, you can only check them out to read, but you can return them and check them out again if you want to reread them as long as you remain a Prime member. All of these have audiobooks that you can borrow and listen to for free if you prefer that. Here's the three scifi short story collections:

The Far Reaches

The universe is bigger than we can imagine

Look outward beyond the stars with six stories from bestselling visionary authors. An AI awakens to its purpose. A researcher seeds a thousand new worlds for one more chance at love. A murder rocks the crew of an interstellar ship. With a sweeping sense of wonder, these stories explore the galaxy...and the horizons of humanity’s potential.

1. How it Unfolds by James S.A. Corey
   
   Spoiler:

   An astronaut’s interstellar mission is a personal journey of a thousand second chances in an exhilarating short story by James S. A. Corey, the New York Times bestselling author of The Expanse series.
   
   Roy Court and his crew are taking the trip of a lifetime—several lifetimes in fact—duplicated and dispatched across the galaxies searching for Earthlike planets. Many possibilities for the future. Yet for Roy, no matter how many of him there are, there’s still just one painful, unchangeable past. In what world can a broken relationship be reborn? The universe is so vast, there’s always room for hope.
   
   
2. Void by Veronica Roth
   
   Spoiler:

   An intergalactic luxury cruise to a distant port is a world unto itself in this piercing short mystery by #1 New York Times bestselling author Veronica Roth.
   
   Traveling faster than light, the transport ship Redundancy is cut off from communication as effectively as an ancient ocean liner. The isolation suits crew member Ace Vance just fine—she’s got nowhere else to be. But when a wealthy passenger turns up dead during a routine voyage, Ace will have to connect with the passengers and crew to uncover the truth. Tragedy will strike again—it’s only a matter of time.
   
   
3. Falling Bodies by Rebecca Roanhorse
   
   Spoiler:

   A young man caught between two disparate worlds searches for his place in the universe in a wrenching short story by New York Times bestselling author Rebecca Roanhorse.
   
   Light-years from home, it’s Ira’s second chance. Just another anonymous student at a space station university. Not the orphan whose Earther heritage was erased. Not some social experiment put on display by his adoptive father. Not the criminal recruited by the human rebels. But when Ira’s loyalties clash once again, two wars break out: one on the ground and one within himself. Which will Ira stand with? Which will take him down?
   
   
4. The Long Game by Ann Leckie
   
   Spoiler:

   An inquisitive life-form finds there’s more to existence than they ever dreamed in an imaginative short story by New York Times bestselling and Hugo and Nebula Award–winning author Ann Leckie.
   
   On a far-off colony, humans tower over the local species who grow the plants they need. Narr keeps the workers in line—someone has to. But when Narr learns just how short-lived their species is, the little alien embarks on a big mission: to find out why their people die and how to stop it. Stubborn and hopeful, Narr has a plan for the locals, for humans, and for the future.
   
   
5. Just Out of Jupiter's Reach by Nnedi Okorafor
   
   Spoiler:

   A revolutionary experiment in space opens a woman’s eyes to the meaning of solitude in a thought-provoking short story by New York Times bestselling, award-winning author Nnedi Okorafor.
   
   Tornado Onwubiko is one of seven people on Earth paired with sentient ships to explore and research the cosmos for twenty million euros. A decade of solitary life for a lifetime of wealth. Five years into the ten-year mission of total isolation comes a consolation: a temporary meetup among fellow travelers. A lot can happen in a week. For Tornado, who left a normal life behind, a little company can be life-changing.
   
   
6. Slow Time Between Stars by John Scalzi
   
   Spoiler:

   An artificial intelligence on a star-spanning mission explores the farthest horizons of human potential—and its own purpose—in a mind-bending short story by New York Times bestselling author John Scalzi.
   
   Equipped with the entirety of human knowledge, a sentient ship is launched on a last-ditch journey to find a new home for civilization. Trillions of miles. Tens of thousands of years. In the space between, the AI has plenty of time to think about life, the vastness of the universe, everything it was meant to do, and—with a perspective created but not limited by humans—what it should do.

I've read the first five so far and enjoyed them all. None of them are tied to each other in any way.

Forward

Take a leap

For some, it’s the end of the world. For others, it’s just the beginning. With brilliant imagination, today’s most visionary writers point to the future in a collection curated by bestselling author Blake Crouch. These stories range from darkly comic to deeply chilling, but they all look forward.

1. Ark by Veronica Roth
   
   Spoiler:

   On the eve of Earth’s destruction, a young scientist discovers something too precious to lose, in a story of cataclysm and hope by the #1 New York Times bestselling author of the Divergent trilogy.
   
   It’s only two weeks before an asteroid turns home to dust. Though most of Earth has already been evacuated, it’s Samantha’s job to catalog plant samples for the survivors’ unknowable journey beyond. Preparing to stay behind and watch the world end, she makes a final human connection.
   
   As certain doom hurtles nearer, the unexpected and beautiful potential for the future begins to flower.
   
   Audible narration by Evan Rachel Wood (Westworld)
   
   
2. Summer Frost by Blake Crouch
   
   Spoiler:

   A video game developer becomes obsessed with a willful character in her new project, in a mind-bending exploration of what it means to be human by the New York Times bestselling author of Recursion.
   
   Maxine was made to do one thing: die. Except the minor non-player character in the world Riley is building makes her own impossible decision—veering wildly off course and exploring the boundaries of the map. When the curious Riley extracts her code for closer examination, an emotional relationship develops between them. Soon Riley has all new plans for her spontaneous AI, including bringing Max into the real world. But what if Max has real-world plans of her own?
   
   Audible narration by Rosa Salazar (Alita: Battle Angel)
   
   
3. Emergency Skin by N. K. Jemisin
   
   Spoiler:

   What will become of our self-destructed planet? The answer shatters all expectations in this subversive speculation from the Hugo Award–winning author of the Broken Earth trilogy.
   
   An explorer returns to gather information from a climate-ravaged Earth that his ancestors, and others among the planet’s finest, fled centuries ago. The mission comes with a warning: a graveyard world awaits him. But so do those left behind—hopeless and unbeautiful wastes of humanity who should have died out ages ago. After all this time, there’s no telling how they’ve devolved. Steel yourself, soldier. Get in. Get out. And try not to stare.
   
   Audible narration by Jason Isaacs (Star Trek: Discovery)
   
   
4. You Have Arrived at Your Destination by Amor Towles
   
   Spoiler:

   Nature or nurture? Neither. Discover a bold new way to raise a child in this unsettling story of the near future by the New York Times bestselling author of A Gentleman in Moscow.
   
   When Sam’s wife first tells him about Vitek, a twenty-first-century fertility lab, he sees it as the natural next step in trying to help their future child get a “leg up” in a competitive world. But the more Sam considers the lives that his child could lead, the more he begins to question his own relationships and the choices he has made in his life.
   
   Audible narration by David Harbour (Stranger Things)
   
   
5. The Last Conversation by Paul Tremblay
   
   Spoiler:

   What’s more frightening: Not knowing who you are? Or finding out? A Bram Stoker Award–winning author explores the answer in a chilling story about identity and human consciousness.
   
   Imagine you’ve woken up in an unfamiliar room with no memory of who you are, how you got there, or where you were before. All you have is the disconnected voice of an attentive caretaker. Dr. Kuhn is there to help you—physically, emotionally, and psychologically. She’ll help you remember everything. She’ll make sure you reclaim your lost identity. Now answer one question: Are you sure you want to?
   
   Audible narration by Steven Strait (The Expanse)
   
   
6. Randomize by Andy Weir
   
   Spoiler:

   In the near future, if Vegas games are ingeniously scam-proof, then the heists have to be too, in this imaginative and whip-smart story by the New York Times bestselling author of The Martian.
   
   An IT whiz at the Babylon Casino is enlisted to upgrade security for the game of keno and its random-number generator. The new quantum computer system is foolproof. But someone on the inside is no fool. For once the odds may not favor the house—unless human ingenuity isn’t entirely a thing of the past.
   
   Audible narration by Janina Gavankar (True Blood)

Black Stars

A GALAXY OF NEW WORLDS

The sky is not the limit. From an alley in New York to an interstellar wormhole, the path to the future looks different for everyone. These cosmic short stories from some of today's most influential Black authors reveal a universe of possibilities.

1. The Visit by Chimamanda Ngozi Adichie
   
   Spoiler:

   As a powerful matriarchy reshapes the world, two men—old friends—confront the past and future in a bracing speculative short story by Chimamanda Ngozi Adichie, author of Americanah.
   
   One night in Lagos, two former friends reunite. Obinna is a dutiful and unsophisticated stay-at-home husband and father married to a powerful businesswoman. Eze is single, a cautious rebel from his university days whose arrival soon upsets the balance in Obinna’s life. In a world where men are constantly under surveillance and subject to the whims of powerful women, more than Obinna’s ordered and accustomed routine might be on the line.
   
   
2. The Black Pages by Nnedi Okorafor
   
   Spoiler:

   By fate and fire, a being four millennia old is reborn in Mali in a short story of contemporary African life and ancient secrets by the Hugo and Nebula Award–winning author of the Binti trilogy.
   
   Issaka has returned home to Timbouctou and a devastating al-Qaeda raid. His only hope for survival is Faro, a stunning, blue-beaded supernatural entity who rises free from the flames of her imprisoning book as it burns. Compelled to follow Faro, Issaka is opening his eyes to their shared history and the ancestral wisdom of his own past.
   
   
3. 2043...(A Merman I Should Turn to Be) by Nisi Shawl
   
   Spoiler:

   African-descended USians are finally obtaining reparations—underwater. Plunge into the action of a visionary future by the award-winning author of Everfair, with narration by LeVar Burton (Star Trek: The Next Generation).
   
   Five miles off the South Carolina coast, Darden and Catherina are getting their promised forty acres, all of it undersea. Like every Black “mer,” they’ve been experimentally modified to adapt to their new subaquatic home—and have met with extreme resistance from white supremacists. Darden has an inspired plan for resolution. For both those on land and the webbed bottom-dwellers below, Darden is hoping to change the wave of the future.
   
   
4. These Alien Skies by C. T. Rwizi
   
   Spoiler:

   Accidents happen in the strange realms of the African Union system. One of them sends two humans to the far side of a star gate in a thrilling short story of hope, survival, and new dimensions.
   
   Copilots Msizi and Tariro are testing a newly constructed wormhole jump that presumably leads to unsettled habitable worlds. Then an explosion sends them off course, far from where they started and with little chance of ever making it back. Now they’re stranded on their new home for the diaspora. It’s called Malcolm X-b. But they’re beginning to wonder how many light-years from civilization they really are.
   
   
5. Clap Back by Nalo Hopkinson
   
   Spoiler:

   A past struggle for racial equity could achieve a profound future victory in this audacious short story about technology, hoodoo, and hope by a Nebula Award–winning author.
   
   Burri is a fashion designer and icon with a biochemistry background. Her latest pieces are African inspired and crafted to touch the heart. They enable wearers to absorb nanorobotic memories and recount the stories of Black lives and forgiveness. Wenda doesn’t buy it. A protest performance artist, Wenda knows exploitation when she sees it. What she’s going to do with Burri’s breakthrough technology could, in the right hands, change race relations forever.
   
   
6. We Travel the Spaceways by Victor LaValle
   
   Spoiler:

   Otherworldly interference in real-world New York City? Or delusions? For the answer, follow two loving strangers in an astonishing short story of faith and hope by a World Fantasy Award winner.
   
   Grimace is a homeless man on a holy mission to free Black Americans from emotional slavery. His empty soda cans told him as much. Then he meets Kim, a transgender runaway who joins Grimace on his heroic quest. Is Grimace receiving aluminum missives from the gods, or is he a madman? Kim will find out soon enough on a strange journey they’ve been destined to share.

It looks like there's at least a few more scifi & fantasy series available on the main Amazon original stories page. Andrew Barrer's Young Blood trilogy, the Faraway collection of fairy tales with new twists, and a serialized novel by Guillermo del Toro and Chuck Hogan called The Boy in the Iron Box. Unfortunately that page doesn't include science fiction and/or fantasy as a genre you can search, so I don't know if this is all of them or not.