I used an Asus Android tablet (Android 7, it was OLD) with a giant SD card +& Moon+ Pro reader app. It syncs reading progress & bookmarks via Dropbox, WebDAV, or Google Drive. I moved to a Fire 10 that I added Google Play Services to. It can sync with my phone or any other Android device. I don’t bother with calibre-web as I don’t have a PC I can keep turned on 24/7 yet, so I just copy over my Calibre library to the SD card. 15k books, 512 GB SD card with ~300 GB left. Moon+ does take a bit to add new books to its database after I think 10k books.
I used an Asus Android tablet (Android 7, it was OLD) with a giant SD card +& Moon+ Pro reader app. It syncs reading progress & bookmarks via Dropbox, WebDAV, or Google Drive. I moved to a Fire 10 that I added Google Play Services to. It can sync with my phone or any other Android device. I don’t bother with calibre-web as I don’t have a PC I can keep turned on 24/7 yet, so I just copy over my Calibre library to the SD card. 15k books, 512 GB SD card with ~300 GB left. Moon+ does take a bit to add new books to its database after I think 10k books.