The biggest issue I have with BookLore is it doesn't have an Android app that syncs automatically where you last left when reading on desktop. (And KOReader - at least from the app stores - can't be used on Android 15, is an incredibly ugly UI/UX, and the latest version doesn't seem to even work with BookLore.) Without that, I don't see the reason to switch from calibre.
Edit: An Android app without an account. There appears to be Kobo integration but Kobo requires an account.