Hi @samuelgerevini,
odrive can link to OwnCloud and NextCloud using the WebDAV integration (https://www.odrive.com/links/webdav).
There is documentation here for OwnCloud: https://doc.owncloud.org/server/latest/user_manual/files/access_webdav.html
And here for NextCloud: https://docs.nextcloud.com/server/15/user_manual/files/access_webdav.html
Please note, though, that odrive cannot sync one link to another, so your original plan of trying to sync your OwnCloud/NextCloud to Dropbox or Google Drive wouldn’t work, at least directly. If you are hosting your own though, and have access to the underlying data, it would be possible to sync that data to cloud storage.