You need to leave Pi-Hole on port 53 if you expect other DNS clients to find and use it.
I have run into this, with Incus wanting port 53. I suspect (but I have not had time to actually do this fix) I can get Incus to only bind to port 53 on certain interfaces and leave port 53 open for Pi-Hole on the public interfaces. Once I get it working I will post how I do it.