Can anyone recommend a good one?
I’d like one that can kinda “save” my progress not only locally. Maybe an app account or something that integrates with a cloud service?
I had an ancient one very early in my smartphone days, but as I lost/had my phone stolen I would lose all my progress and miss the pages of the books I was reading.
Not FOSS, but Lithium on the play store has what you need and the app is free of tracking and ads.
I find open-source apps in this department to be still lacking.
It is not possible to make free open source app without tracking to save in the cloud.
“Book Reader” from f-droid has “sync folder” option, but I never tested it. I guess of you sync that folder with some other app (like syncthing, or google drive) you can have it in other places.