…I acquired this domain and installed wordpress, this site was suddenly out of order. I haven’t changed anything functional, so I had no clue about it.
Hmmm…
After a bit of log inspection, I had the solution. The DNS propagation had fulfilled its work and the IPv6 entry was active! All of my domains only used IPv4 before, so I forgot to activate the IPv6 listen entry in the Apache configuration.
<VirtualHost 5.9.28.144:443 [2a01:4f8:161:108e::2]:443>
ServerAdmin webmaster@heppi.dev
ServerName heppi.dev
...
I fixed that, restarted Apache and voilà…
Tada, my first IPv6 site is online. This was easy, so I will change all of my domains soon.