I have, and the technical support representative at Proton confirmed
it, but not without implying that it was my fault for using rclone. I
asked the official recommendation for Linux users to do automated or
scriptable backups onto a Proton drive and the answer was that some
kind of SDK was planned for the future. Proton drive stopped working
completely with rclone shortly after that, which was about two months
ago.
To be honest, all consumer cloud storage providers get touchy when you access them via API.
Dropbox API refuses to sync certain 'sensitive' files like game backups (ROMs or ISOs). There is no way for Dropbox to know if you own the game and thus can own a backup, they just play file police.
