I was just trying to play with the systemsettings5 > display configuration > global scale parameter.

Initially, it seems to work nicely (in comparison to my current method, using font dpi modifications)
BUT
If you start konsole, you get - depending on your cursor position - single pixel black lines across the konsole window. (sometimes only line fragments and many pixels instead of a line)

My konsole config:
- black font on white background, dejaVu sans mono 9pt, smooth fonts, draw intense colors in bold

I didn't try other fonts though, but this is still very annoying for this scaling feature and does never happen by just manipulating the font dpi.

Any suggestions?