Dyndns and Ressource Records

[Markibot]

Hi,
I run Opnsense directly behind a Docsis-modem on a Comcast Xfinity line. Its dual stack, Opnsense gets an Ipv4 and an IPv6 address, also with prefixes for the local nets. Everything works as expected so far.

I want to make certain services publically available. So I set up a domain with Google Domains and also set up a dynamic DNS hostname. You'll receive a username and a password which I used in Opnsense under Dynamic DNS.
So far so unexciting. I used googedomains as Check IP Method.

Now however. if I disable IPv6 on the WAN interface in Opnsense (e.g. enforce IPv4), Opnsense registers with an A record at Google. If I enable IPv6, and have a dual stack configuration on the WAN interface. Dyndns only registers a AAAA record and no A record anymore.

In Opnsense (at least in the GUI) I don't have a choice what kind of record should be registered.

My question is now, how to register a A record if IPv6 is enabled? I also don't know if this is an issue with Opnsense or Google (or both).