I'm building a plugin for Obsidian called Relay that makes Obsidian real-time collaborative [0].

It isn't end-to-end encrypted (yet), but you can self host the document collaboration server on a private network (like tailscale).

If you're like me and you need real-time collaboration and privacy but e2ee isn't a strict requirement for your collaborative docs then you might enjoy it.

I also use Obsidian sync for e2ee device sync -- it is a fantastic product.

[0] https://relay.md