I sync Joplin via Dropbox across phone and 2 laptops. In theory a prob? But in practice rare to never bc im only one user on one device at a time. And im making small changes at a time. There was 1 minor conflict once and Joplin saw it and i quickly resolved it.

What's the issue? I guess it's just as simple as uploading the .db?

You're changing some note on device A and the same note differently on device B.

Both sync. You now have a conflict.

With text files, you at least have obvious merge strategies. With SQLite it isn't quite as easy.

I still don't mind SQLite in Joplin. It has advantages, as well.

Ah the multiple devices issue. I see...

How about doing everything server side so you are just using a thin client (read: web browser) instead?

See trilium: https://github.com/zadam/trilium