> I used Nextcloud sync in the past, but found it unreliable.

What was wrong about nextcloud sync? I'm just about to set it up for myself.

The sync would stall and I'd have to go retry, or it would fail with no error clear message. In the end, I had no idea what had really synched correctly. The app was unhappy if I deleted a photo too quickly.

With Syncthing, I sync to a directory that my Nextcloud user can access (a read-only mount), so I can still easily share photos using Nextcloud, for example.

(although it's unfortunate that the Android syncthing app is being retired. h/t for the heads up and the recommended alternatives)