My system:
Operating System: openSUSE Leap 15.3
KDE Plasma Version: 5.24.3
KDE Frameworks Version: 5.92.0
Qt Version: 5.15.2
Kernel Version: 5.3.18-150300.59.54-default (64-bit)
Graphics Platform: X11
Processors: 12 × Intel® Core™ i7-10850H CPU @ 2.70GHz
Memory: 31,2 GiB of RAM
Graphics Processor: Quadro RTX 3000/PCIe/SSE2
Force font DPI: not checked

Running LibreOffice with the above mentioned DPI setting produces the menu font nicely readable, however, all other LO fonts including open menu or save menu are so small that are almost unreadable. Changing Force font DPI to any arbitrary number makes no change to LO but to the size and aliasing of icons. The only solution I have found is to create a file with the following lines
#!/bin/sh
export SAL_FORCEDPI=120
libreoffice

Changing Force font DPI to 120 makes no difference as to the LO. All other software installed response correctly to DPI setting.
Is this weird behaviour related to Plasma or it is related to LO.

Thank you for any help.

Bojan