Check out koreader for Kobo devices. I've been using it for a quite some time and it adds some nice Calibre features such as wireless sync. Besides that the PDF support is leaps ahead of stock Kobo
You might know already, but https://www.protondb.com/ has user reports for Proton games, the reports often include tweaks if a game doesn't work without tweaking.
https://github.com/koreader/koreader