If I set `export PLASMA_USE_QT_SCALING=1` in ~/.bash_profile KDE Plasma, global
menu just stop working. It only shows a empty application menu bar on the top
of the screen. When I remove `export PLASMA_USE_QT_SCALING=1` in the
environment variable, global menu is back to normal. 

On my PC, I have encountered this bug on several KDE versions from 5.20 to the
current 5.23 on Tumbleweed. In the past, I didn't have the same issue on
Manjaro KDE when I enabled this environment variable. Also, I didn't encounter
this issue when I use KDE on my virtual machine and it only happened when I
used KDE installed on my PC.

Therefore, I don't think it's a upstream KDE issue. Could Tumbleweed KDE
maybehave some hardware compatibility issues that other KDE distro don't have?