There is an iOS “Audiobook” Version with support for muliple bookmarks. The Android Version stores the position where you stopped before and continues there. If you play a different File, the Position is lost (AFAIK).
Give it a try, it is the only Music App with Playlists etc with Nextcloud integration. If it not fits your needs, you always can change to offline solution.
I just tried the app and like it, but will resort to a dedicated offline audiobook player then so I don’t lose track of my audiobooks.
The offline audiobook player I’m using also detects chapters in the mp3 file.
There are some more options:
the music App is broken since 26 but there is a commit with a fix. You can apply the commit (or wait until it is updated by the maintainer) and then you can use the “music” app as an Ampache/Subsonic Server. Then you can use one of these Ampache clients and/or one of these Subsonic clients
Not all clients work with all android versions but they have nice features, such as bookmarking etc.
I am very confident that you will find a client that fits your needs.