I am using researchxxl's fork now and it works fine, had 2 updates in the meanwhile
F-Droid
F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.
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https://github.com/researchxxl/syncthing-android/commits/main/
Catfriend seems to be still contributing to this fork
Interesting. So while the handover was pretty bad, I think this is the version to go with
Syncthing itself is fine. The unofficial Syncthing for Android was the problem.
You can get around the problem by installing Termux and using the official Syncthing client.
Using termux full time for running network facing services is pretty insecure. Termux should not be relied on for sensitive things, EVERY process runs as the same user.
There is also the android version of syncthing-tray
https://martchus.github.io/doc/syncthingtray/docs/android.html
https://martchus.github.io/syncthingtray/#downloads-section
https://martchus.github.io/doc/syncthingtray/docs/screenshots.html#mobile-ui-on-android
That dev has been around for a long time so seems like a decent option even if not as polished as syncthing-fork was.