@Dave It actually works quite nicely with Tresorit. And the latency lag is acceptable.
I've been doing this via Rclone + Jotta Cloud with Rclone encryption, which still works better than Rclone + Proton Drive. But not as smooth as Tresorit. Rclone + Backblaze B2 + encryption is also better than the Proton Drive approach.
I've also used this approach in read-only mode with @borgmatic too, which is a great way to restore data from a backup. And that's almost as smooth as Tresorit (even though a very different use case).