Bug 408978

SUMMARY
systemsettings would add redundant ",Regular" to a font selected to kdeglobals, making applications unable to use the genuine bold/italics variants provided by the font.

For example, on my system, when I use systemsettings to change the default font, programs are forced to used a generated bold version of the font. The results are very poor.
kdeglobals: https://pastebin.ubuntu.com/p/5SxRdrCfFD
Screenshot: https://imgbox.com/qJDoQ3Oh

But if I remove those ",Regular"'s by hand, as is shown in the screenshot, the outcome is much better, because programs can use the Bold weight provided by Noto Sans itself.
kdeglobals: https://pastebin.ubuntu.com/p/nPkjy8CWBs
Screenshot: https://imgbox.com/PXXCz6l6

SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.16.1
KDE Frameworks Version: 5.59.0
Qt Version: 5.12.4