I have had Pi-Hole running as a docker container on a Synology NAS for several months. I followed with some modifications the excellent guide by Tony Lawrence (Free your Synology ports for Docker | Tony Lawrence).
The Pi-Hole provides DNS to my home network which is delivered with Ubiquiti Unifi equipment. The Unifi controller runs on the same docker host.
I recently deployed a DNS-Over-HTTPS client, also as a docker container, that is used by the Pi-Hole instance as a custom DNS provider. The image and additional details are at Docker Hub.
I thought this might be of interest to the community. Please let me know if you see any problems, incorrect or misleading or confusion information in the write up on Docker Hub.
thanks
Brad