Agree would be good to add, currently you can already just setup the DNS records with AAAA to point to the Cloudron and that should work fine. I think the automation of that is just what is lacking, next to maybe some mail DNS record related things, but not 100% sure.
Given that ipv4 is supported everywhere and at least I am not aware of a VPS provider who does not give ipv4 addresses, we have handled that as low priority so far.
I am curious in which circumstances you have ipv6 only clients? Maybe we are missing a crucial use-case.