StoryBundle has a new bundle with complete trilogies, curated by Lavie Tidhar.
I just got the two sequels to Aliette de Bodard Aztec trilogy from that new ebook store, so I guess I caused this....?
https://storybundle.com/trilogies
I have most of these, and haven't read any of them, which is my special superpower.
Rupert Wong, Cannibal Chef by Cassandra Khaw
Obsidian and Blood by Aliette de Bodard
Machineries of Empire by Yoon Ha Lee
The Worldbreaker Saga by Kameron Hurley
The Bookman Histories by Lavie Tidhar
The Complete Machine Dynasty by Madeline Ashby
The Axiom (starting with The Wrong Stars) by Tim Pratt
The Tao Trilogy (starting with The Lives of Tao) by Wesley Chu