I tried an external 2.4 GHz-only dongle which gets me just as far as the builtin WiFi. I tried with a wpa_nf in the boot partition. Signal strength is 1 bar below full signal strenth. The network icon on the desktop doesn't even change at all on any connection attempt. And the router has band steering enabled. It's noteworthy that the little '5G' icon is shown in the network list.

I even copied the password out of a known good.

I thought maybe wrong password but no matter how hard i tried it would fail the same way again. Selected it, typed the password and after around 30 seconds it failed to connect. It showed the WiFi networks around my home and my own one fine. I followed the first time setup normally. Latest Raspian Buster (without recommended software). Wireless mouse (needs 'usbhid.mousepoll=0' to work properly) connected to the other USB 2.0 port. Wired keyboard connected to a USB 2.0 port. Legit 64GB SanDisk Ultra microSDXC card (A1) fully tested (including overwrite) with f3.ġ080p 60 Hertz LCD monitor connected to the port next to the USB-C port (HDMIHDMI). Heatsink enclosure (open at antenna location). Everything seems to work except for WiFi.