So here is my setup. I have a Raspberry Pi3 b+ setup with Ubuntu on it, which has docker installed. I then use that as an app server that runs a few containers; Home Assistant, Pi Hole, MQTT Broker, etc).
My Pi Hole container works great and I have my router pointed to use the app server's IP pi hole, pi hole uses it with a handful of ports passed to the container. If I go to my app server IP. Let's say 192.168.86.20 I can get to pi hole see the graphs, the blocked content etc. However, It only shows my router as connected (it also shows the app server "localhost"). But all of my computers, TV, smart devices don't show. they are being considered as part of my router.
I use a Google OnHub (TP-Link version), You assume it would pass its local domain list to the pi hole so you could see what is making the request.
There as to be some way without altering each devices network settings to point to pi hole.