[svennek]

I would use syncthing, which is open source at https://syncthing.net/.

After minimal setup, it just works(tm).

You have a normal directory in your filesystem, that is synced to the other peers (which you set up in the "minimal setup").

I have been using it for years, and it works well. It has no problems crossing os'es (i.e. windows -> linux, linux -> mac)

For windows I usually recommend https://github.com/canton7/SyncTrayzor, but vanilla syncthing works fine too (but don't try to mix them!)

[wdfx]

Have you had any concern exposing your syncthing on the internet?

[svennek]

No.