I went through the reported bug (and also commented on that bug):
It looks like it is an intended change in Qt that makes the existing configurations not work anymore, I’ll summarize it as how I understand it:
PREVIOUSLY:
- you have an installed font with nerd icons
- even if you use a font (not nerd, nor patched) that does not provide nerd icons, Qt will look for a font providing that and use that
NOW:
- It is not rendered if the current font does not have a nerd icon.
That seems to be intentional (https://code.qt.io/cgit/qt/qtbase.git/commit/?id=a44b6950268214d802bc7ce7df09975261263e31)
For example, concerning what @anon49550902 said: maybe “FiraMono Nerd Font” does not provide a specific glyph. Previously, that was rendered taken that missing glyph from another nerd font providing it. Now, that does not happen anymore. On the contrary, “Agave Nerd Font” provides all the needed ones.
As another example (see my comment on the bug):
- install
ttf-hack-nerd - set the “Fixed width” font in System Settings to “Hack Nerd Font 10pt” (the default is “Hack 10pt”)
- make sure your Konsole profile does not specify any font (see the corresponding “.profile” file to be sure) and nerd icons will be shown correctly
- same for Kate
If you specify, or you had previously specified, any font in those configurations (even “Monospace”) it will still not work. You might have to manually modify the Konsole profile file and .config/katerc and remove the setting for the font.
I haven’t stressed that in my initial post: this “bug” (well, the “new intended behavior”) is only for Qt/KDE applications. For example, Alacritty still works without any intervention.