I have used both used GitHub for sync and Syncthing. Both work pretty flawless, but I prefer Syncthing (or rather Syncthing-fork).
As far as I remember, synching to mobile is not easy with the GitHub solution (I only used it to sync between two desktops), but Syncthing works great on both mobile and desktop.
Can you switch to scaled at all? I’ve been looking for that since my instance was updated.