I run pihole without any problems as a docker container. I assume you want to ask how well it works to add custom records, because that’s what you usually do with a dns server.

Adding single records with the web ui works just fine. However, adding wildcards isn’t possible. So you end up attaching a terminal to your container and adding dnsmasq configs yourself. This is a bit poor.

On the other hand: How often do you need to add wildcards? I needed like 2 entries since I set up pihole a few years ago.