Comment # 11 on bug 1206281 from Daniele Granata

Operating System: openSUSE Tumbleweed 20230626-2367.1
KDE Plasma Version: 5.27.6
KDE Frameworks Version: 5.107.0
Qt Version: 5.15.10
Kernel Version: 6.3.9-1-default (64-bit)
Graphics Platform: X11
Graphics Processor: NVIDIA GeForce GTX 1660 Ti/PCIe/SSE2
NVIDIA 535.54.03-10.1

Setup:
notebook + external monitor on HDMI or DP.
KDE Plasma settings:
Notebook monitor off when external monitor connected.

What is working:
suspend and resume with attached monitor on battery and not (using Plasma
greeter)
suspend and resume with NO attached monitor on battery and not (using Plasma
greeter)
switch off and on the monitor
unplug and replug the monitor cable (display port)

What is NOT working:
leave the notebook on battery with NO attached monitor and wait until it goes
to sleep
or leave the notebook on battery with NO attached monitor and close the lid
there will be no resume, black screen, the CPU/GPU fan goes crazy, no ctrl+F to
switch to terminal,
no ctrl+alt+backdel to kill xorg
I have to hard power off the PC.