Issue when installing on vanilla RPi4 + Bullseye Desktop installation

[rpi-tom]

Attempting to install and run on RPi 4 with vanilla Bullseye installation.
The screen lights up white, and I can see the touchscreen is working when I run in dual screen mode and touching the hat screen moves the mouse on the HDMI screen, but I have got nothing but a blank white screen from the hat.
Is this hat compatible with RPi 4 and the latest Bullseye release?

[tvoverbeek]

Bullseye has changed the way these displays are controlled. Procedure needs to e adapted for Bullseye.
For now use Raspberry Pi Os Legacy (= Buster)

[rpi-tom]

I have just retried this by building a fresh Buster and trying to install. Still no luck and a blank white screen.
Desktop Image installed via Raspberry Pi Imager choosing Buster Desktop install.
Diagnostics below. Is there any other information that would be useful?

pi@raspberrypi:~ $ apt policy raspberrypi-kernel
raspberrypi-kernel:
Installed: 1:1.20211201buster-1
Candidate: 1:1.20211201buster-1
Version table:
*** 1:1.20211201~buster-1 500
500 http://archive.raspberrypi.org/debian buster/main armhf Packages
100 /var/lib/dpkg/status

Linux raspberrypi 5.10.63-v7l+ #1496 SMP Wed Dec 1 15:58:56 GMT 2021 armv7l GNU/Linux