Any opinions on OpenCloud.eu ?

This is a "nextcloud" or "owncloud" alternative. Its origin was as a fork to owncloud infinite scale (ocis), so it's shares the underlying feature set (written in Go instead of PHP, being lenient on resources and usable on a raspberry pi 4B.)

The latest release (2.0, see link) leverages PosixFS so instead of having to manage a database, you can rely on snapshots (on the filesytem) for all your backups.