Comment 32 for bug 1944397

@waveform The issue might be with the bcm2711-rpi-4-b.dtb...

sudo dpkg -i linux-firmware-raspi2_5-0ubuntu0~21.04~ppa1_arm64.deb ; sudo flash-kernel --force 5.11.22-9021-raspi ; sudo reboot

Result: no video.

sudo dpkg -i linux-firmware-raspi2_5-0ubuntu1~ppa1_arm64.deb ; sudo flash-kernel --force 5.11.22-9021-raspi ; sudo reboot

Result: no video.

cd /boot ; sudo cp dtb-5.11.22-9021-raspi /boot/firmware/bcm2711-rpi-4-b.dtb ; sudo reboot

Result: Video!

sudo flash-kernel ; cd /boot ; sudo cp dtb-5.11.22-9021-raspi /boot/firmware/bcm2711-rpi-4-b.dtb ; sudo reboot

Result: Video!

So maybe there's an issue with the bcm2711-rpi-4-b.dtb which the newer firmwares are installing causing issues with the newer kernels?

Working firmware versions I am seeing that work with the older 5.11 bcm2711-rpi-4-b.dtb:

sudo vcgencmd version
Aug 31 2021 14:52:47
Copyright (c) 2012 Broadcom
version 67615e950e1e28b92dfae6303cf7a8b879a8908f (clean) (release) (start)

sudo vcgencmd version
Sep 30 2021 19:21:03
Copyright (c) 2012 Broadcom
version 51215b4f6e3966401ecd99652a35cf1c25069113 (clean) (release) (start)