I spent some time on this today and feel that I'm pretty close! I've got all the hardware in place, I am able to tune into and record from the HDMI. The output displays fine using this custom channel:
#EXTINF:-1 channel-id="HDMI" channel-number="100.1" tvc-guide-placeholders="86400",HDMI
http://10.0.1.171:80/main
Now I'm trying with the androidhdmi-for-channels program to get it to change channels on the AndroidTV dongle automatically. I followed the instructions to install on my Mac mini server, the same one with Channels DVR installed. I'm using this Custom Channel format which I gleaned from above:
#EXTINF:-1 channel-id="msnbc" channel-number="100.1" tvc-guide-placeholders="86400", MSNBC
http://10.0.1.171:7654/play/tuner/msnbc
...but I'm getting this error when I try to tune in:

I do have Developer Options and USB debugging enabled on the Android TV dongle too. I also installed add on the Mac with the brew command. Is there anything else I need to do in order to get adb working and connected from this Mac?
I thought it might be a macOS Ventura / permissions thing but I made sure this was allowed.
Any feedback or suggestions to try are appreciated!