Syncthing can work. You don't get the centralized server though. Well you can run it on an always on system. I'd like this to be a VPS, but the files sit on the VPS in clear text. I like syncthing as it syncs file mode bits as well.

Resilio Sync is decentralized as well. And lets you setup encrypted folders, so only peers with the password can decrypt them, but other peers can take part in the syncing. So I can run an instance on a VPS and not worry too much if it gets compromised. I find its Linux support lacking and wasn't as reliable as Syncthing for me. I'm going to try it again sometime.

Seafile. Centralized server, can do encrypted folders. I'm going to look at this one again, but found the sync took a real long time, and I don't think it synced file mode bits.

Nextcloud. Centralized server. Can do encrypted folders. Seemed OK, but didn't do mode bits.

Currently I'm using Syncthing, where my central always on machine is my home server which would be running anyways. I like the idea of having a 'central' server in the cloud, but need that to be secured in a way that Syncthing can't do. So I'm not sure its my permanent solution yet.

I also use Unison for much larger folders, like my code directories.