How do you sync Music and Playlists locally?

I have tried looots of Music apps, Both Android and Linux.

I currently go with Anrimians Music Player on Android.

On Linux I simply use VLC Flatpak, and currently for the 4.0 “beta” I use Distrobox with an Ubuntu 22.04 Container and their PPA. The latest VLC Flatpak should have the FLAC stuttering issue fixed though.

So my problem is this:

as I find Playlists weird on Linux, I always focusser on folder-baser Musicplayers
but duplicating songs is not possible there, so I restrict the possibilities a lot
I would like to sync most music between phone and Laptop using Syncthing, and also the Playlists.

Now I wonder how this would work. For simplicity my sync structure currently is:

#Android
/storage/emulated/0/--SYNC-- 
#goes to
/home/user/Handy-Backup/--SYNC--

#Android
/storage/emulated/0/Music
#goes to
/home/user/Handy-Backup/Music

I hate how Android handles permissions for the Music folder, how all apps use it etc, because its more of a pain to sync. But all the Playlist .m3u files land here.

What would be a way to sync the Playlists AND the music folder and have it work? How do m3u files work, do they use variable Directories like “in this folder, subfolder ALBUM1”?

Thinking about that I guess it would be best to put all music into Android Music folder, right? As the M3U files are probably referring to files in the same dir then and everything works.