Mullvad’s recent audit by Assured AB was a bit concerning to me. Fail2ban and user-writable scripts running as root is not the sort of thing I’d expect in a service whose only job is to provide a secure relay.
Avoiding and guarding root should be Sysadmin 101 material.
I recommend any amateur Linux admins read audit reports like this. While some low-priority recommendations are a but cargo-cultish, most advice is pretty solid. Frankly, much of this is the sort of thing a good admin should catch well before a proper audit.