A way to get Mac seeing HomeKit Live Video

For years, I've just come to accept that the Home app on my Mac just can't seem to see live video from HomeKit cameras. It can show me past clips. My iPhone and other devices can see the video. But no live video feed on Mac. Today, after adding a HomeKit-enabled doorbell, I finally tried to figure it out again, and eureka! I finally hit on the solution.

Short version: if you have a Wifi router/mesh device separate from your ISP's box, do not connect your Mac ethernet directly to the ISP box. Connect the Mac's ethernet to the Wifi/mesh device instead.

Long version: I have an AT&T FiOS box with a TP-Link Deco mesh network device connected to it to distribute the WiFi signal. I let the AT&T box handle NAT because it seems impossible to make the AT&T box let the Deco handle it without creating a double NAT situation. Anyway, I had been connecting the Mac directly to the AT&T box via ethernet cable instead of connecting it to the Deco, which meant that the Mac was connected to a different router address/subnet than everything else on the mesh network. Today, I plugged the Mac's ethernet cable into the Deco instead, and immediately was able to see the live feed from my cameras.

I came across quite a few posts with different solutions involving mics or restarting things, etc., but I hadn't seen this solution before. So I just wanted to share in case somebody else finds it useful.