Hope I’m not too late, but this list may help:
https://www.penguinrandomhouse.com/ebook-deals/?
It’s not exhaustive though.
I got The Supernatural Enhancements by Edgar Cantero for free. As well as others on this list.
Zadie Smith’s Feel Free is included, as is Mouthful of Birds by the amazing Samantha Schweblin.
What a lovely surprise, to get free books!