Hi There,
I run Two CasaOS Servers and on them I also Run Pi-Hole. I have been looking at Setting up some sort of HA to keep the Configs in sync. Actual HA is Stupid hard. I am still learning Docker and found Something called Orbital-Sync, Which is supposed to be an easy way to sync multiple Pi-Hole Configs.
I managed to get it working. I am lucky enough to have a spare Raspberry Pi so got it working on there, then pulled it as a standard docker container. Then got CasaOS to rebuild it so it is in the GUI. It is GUI-less so there really is not much reason to add it into CasaOS but if you want I could export the Details.