OpenCloud is pretty cool. I use Samba for my file management, but I set this up so my users could have a Google Drive alternative.
It is really great though, better than it's competitors (NextCloud, OwnCloud, etc.) in my opinion. They're old and crusty.
At the moment (2026-06-04) I haven't set up any Collabora or Only Office type of integrations so I don't know if they'd work. I have one issue with Opencloud, which is that they require the usage of 3-4 separate, defined client-ids for use with oidc authentication. They have a separate client id for web, ios, android, and desktop client applications, and that just really grosses me out for some reason. here's the ithub issue: https://github.com/opencloud-eu/opencloud/issues/1441