Our website is hosted with loopia at mydomain.com, but we also have a webapp running on Google App Engine which we would like to run on subdomain.mydomain.com.
We also have a couple of other subdomains running, but those are simply referred to via the IP address.
I have followed the steps at https://cloud.google.com/appengine/docs/standard/python/mapping-custom-domains#dns_update. The Domain Mappings consist of four A, four AAAA and one CNAME records.
When I try to add all of them to mydomain.com (the documentation isn't clear if this should be the domain or subdomain), I get an error saying there are colliding records. When I try to add them to subdomain.mydomain.com, I'm able to add either the A's and AAAA's or the CNAME, but not both, or I'll get a colliding record error again.
In both cases, subdomain.mydomain.com just displays a Google backed 404 error, while myapp.appspot.com is working without problems.
This is very similar to this question, except that we're not using Google as our registrar.
How do I properly set up the DNS records so that the subdomain points to my webapp?