@gemlog I don't know what DNS GUI Contabo had, but Hurricane Electric has free DNS: https://dns.he.net/
Not too flexible, but it suits my needs.
And they support dyndns updates in case your IP changes.
They also have a nice IPv6 tunnelling service, there was some gimmick to get the SMTP port open though — I don't remember exactly, but you had to pass some test and email them to ask for that explicitly, so it's possible.