Backups is the keyword. I run Vaultwarden on my internal network, the data gets backed up to an external hard drive, borgbase and another remote machine using borg backup. I also stored the passphrases for these backups in a KeePass database (that is backed up elsewhere). I don’t think I need to worry about data loss. Plus - if the Server is not reachable the synced devices should still have access to the passwords.