I only host Nextcloud in an old setup (read pure PHP, MariaDB, Apache - no docker, etc.)

That server is set-up to be snapshotted daily. Also there’s a script running about 30 min before each snap shot that will also dump the database to disk (as otherwise the snapshot might contain a random state of the database). It’s not perfect, but it works - also because everything of this is done in the night, when I do not use the system, so chances are really low, that the snapshot of the disk and the database dump in it are not desynchronized too much.

I do not know what’s the best practice for a modern Nextcloud setup with docker is or how to handle the other two…