export PLASMA_USE_QT_SCALING=1 in environment variable makes KDE buggy

When I tried KDE Plasma 5.22 I found some strange bugs:

  1. Global Menu was not shown on the menu bar.
  2. When I deleted the task bar and added the new one, pressing the super key couldn’t open the application menu any more.
  3. Switching the touchpad from reverse scrolling to natural scrolling got reset after restarting new session.

Then I found the culprit was because I put export PLASMA_USE_QT_SCALING=1 in ~/.bash_profile to improve HiDPI on KDE Plasma. After deleting this environment variable all of the issues above disappeared. Is this an OpenSUSE exclusive issue? I remember one and half year ago I didn’t have any of the issues on Manjaro KDE when I enabled this environment variable.