Have you tried the built-in Books app on iOS? I find it to be a simple book reader that allows for ePub files to be opened from the Files app without having to sync them manually using something like a Mac.
I have not, I still consider myself a iOS newbie and tend to avoid the Apple software because of their lack of features and usefulness. But I'll give Books a try, didn't realize it let you read local files, thanks a lot for the recommendation! :)
Apple Books is actually pretty good if you have epub. I have used it a fair bit in the past (I now use a Kobo, or physical books primarily). But Apple Books was the best I found on iOS. There were some others that were pretty good but they seem to be unmaintained and/or do some weird things that I didn't particularly like so I went back to Apple Books.
Gave Books a quick try, hardest part was probably how to send files from Linux to iOS, but thanks to ifuse it ended up being pretty easy, by (ab)using Chrome's download directory. Still haven't found a way of importing them into Books automatically, but better than nothing I suppose.
In case others are in the same situation, I ended up doing something like this:
idevicepair pair
mkdir ~/iphone
ifuse --documents com.google.chrome.ios ~/iphone
cd ~/iphone
cp /home/user/books/*.epub .
cd ~
fusermount -u ~/iphone
Then use Files app on the phone, navigate to the Chrome documents folder and click on the .epub file and after ~5 seconds or so it opens up in Books, and after that it's accessible via Books directly.
I usually just have mine in the Safari downloads folder. Then use Files to open them.
If you’re on Linux, using iCloud to add files there should be easy enough as well. Then I just added them as I needed them. I’m on a Mac though so it’s a bit easier.
I have not, I still consider myself a iOS newbie and tend to avoid the Apple software because of their lack of features and usefulness. But I'll give Books a try, didn't realize it let you read local files, thanks a lot for the recommendation! :)