But Syncthing Fork is not shut down and is still maintained (never used the main version tbh).

https://github.com/Catfriend1/syncthing-android-fdroid

https://f-droid.org/packages/com.github.catfriend1.syncthingandroid/

I’ve used Joplin before which was okay-ish (but borked the e2e encryption during an update).

Now I would recommend Silverbullet if you are really keen on self hosting a notes app.

But the notes that work best for me is simply Obsidian + Syncthing-Fork (you could self host a syncthing server), thanks to its sheer ability to adapt to nearly any use case thanks to its plugin.