I have several remarks for Hetzner:
- any vps is ok, the lightest will aready work
- however, if you use ARM, you might run into issues, see e.g. Using MIAB On ARM You might be better off using x86
- I think Hetzner blocks port 25 (which you’ll need for mail) by default. Once you have paid the first invoice (after a month or so) you can ask them to open the port. It’s up to you if this is an issue for you. If you are already a customer they will probably open it directly as I think this is a per account setting, not per vps.
- no special installation remarks, just follow the MiaB manual
- you can use mail.mydomain.com, just insert that instead of box.mydomain.com