Created attachment 151328 [details] screenshots of System Settings/Appearance/Global Theme using different font configurations When Noto Serif is configured as a font in System Settings/Appearance/Fonts, some bold text is rendered using Display Bold instead of (Regular) Bold typeface. Unfortunately, Noto Serif Display Bold is hard to read at small font sizes (as display typefaces are intended for large typesetting in general AFAIU). Note: When Noto Sans is configured, it seems bold text is consistently rendered using (Regular) Bold. The attachments show the same UI element (System Settings/Appearance/Global Theme) using different font configurations as indicated by the filenames. Note: For the left text, for Noto Sans, “Noto Sans Regular.png” and “Noto Sans Bold.png” look the same (as expected), however, for Noto Serif, “Noto Serif Regular.png” and “Noto Serif Display Bold.png” look the same. Also note that not all bold UI elements seem to use Display Bold when configuring Noto Serif (not visible in the screenshots). The problem was introduced with some update during this year or in the late last year. Unfortunately I do not remember the exact update. Also, a Qt update might have been involved. KDE Plasma Version: 5.25.4 KDE Frameworks Version: 5.96.0 Qt Version: 5.15.5 Graphics Platform: X11
The way font variants get applied is determined by the font, the fontconfig file and the set of installed fonts, not anything in KDE. So there are three options regarding what changed: 1. Noto Serif itsels changed what bold variant it asks for 2. Your fontconfig changed how the font falls back when a variant that doesn't exist on disk is requested 2. Your set of installed fonts changed In both cases, you should ask your distro for help.