for a few days my BP is showing a strange behaviour now: HDMI output does not work any more if I use an HDMI cable , but if I use a HDMI to D-SUB (VGA) adapter, the video output works as expected. Rebooting won't fix it, and the monitor's HDMI input and the HDMI cable are working perfectly. The BP is running on Armbian, Version 20.11.6 Buster, and all updates have been applied.
pi@pi:~$ cat /etc/os-release
PRETTY_NAME="Armbian 20.11.6 Buster"
pi@pi:~$ uname -a
Linux pi 5.4.85-sunxi #20.11.6 SMP Sun Jan 3 21:23:24 CET 2021 armv7l GNU/Linux
Have there been any changes to the firmware recently that could be the reason for this?