I'd be interested in comparing notes.

1. I can't seem to get WiFi working using the HS4-Pi image. I'm about to swap SD cards with a fresh Raspbian image to see if that makes a difference. EDIT: Still didn't work with the fresh image. More testing and research determined that the problem was the fact that my SSID was hidden. I needed an extra keyword in wpa_supplicant.conf, scan_ssid=1.

2. I see a bunch of gpio commands in /etc/rc.local and that doesn't seem like a good idea on the Pi 400. EDIT2: These appear to be for controlling LEDs on the Hometroller. Commented them out since they were messing with the GPIO pins I plan on using for other things.

3. I'm using a UCTronics PoE power splitter for 5V/Ethernet to power the Pi400 off of a Unifi PoE switch. Anyone else doing this? EDIT3: I found the PoE splitter I'm using on the Vilros site being sold as a PoE solution for the Pi4B, which has the same power requirements as the Pi400, 5V @ 2.4A.