HDMI Port - Monitor not detected - Linux Mint 20.2 Cinnamon / Lenovo T450s with Geforce940M / nvidia-driver-470

Linux Mint 20.2 Cinnamon / Lenovo T450s with Geforce940M with latest bios / nvidia-driver-470 (470.57.02-0ubuntu0.20.04.1)

External monitor connected via HDMI is not detected.

Already searched for existing solutions. Nothing worked so far.

/lib/modprobe.d/nvidia-kms.conf => options nvidia-drm modeset=0
cat /sys/module/nvidia_drm/parameters/modeset => N

xrandr -q
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 16384 x 16384
eDP-1-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 309mm x 173mm
1920x1080 60.05*+ 60.01 59.97 59.96 59.93
[…]
320x180 59.84 59.32
DP-1-1 disconnected (normal left inverted right x axis y axis)
HDMI-1-1 disconnected (normal left inverted right x axis y axis)
DP-1-2 disconnected (normal left inverted right x axis y axis)
HDMI-1-2 disconnected (normal left inverted right x axis y axis)

thanks for any suggestions / help