If your cloud storage is supported by rclone, you can use that to mount the storage and then back it up, locally or to an S3 storage at a different provider. That’s how I backup my wife’s and daughter’s OneDrive, using rclone and restic.
This is a very dangerous take - while at this point in time the RTS have not yet been formally adopted by all the relevant bodies, they will be, at which point they will be enforceable.
I find that one concerning in an enterprise setup (which they target). Or the fact that the desktop client has 999 open issues. Or that the last version silently takes you off the stable channel. I could go on … Nextcloud desktop has severe quality control issues.
Full. agree on the data loss issue. I have experienced it myself, and their forum and issue tracker also show this. Its not a « trusted system » at all.
Not necessarily. You can for example configure both Thunderbird and mailcow to allow you to reply from any address (of the domains you manage, of course), without having to create the mailbox.