KDE 6: No fallback font on Konsole (and other applications)? (Fedora 40)

(This is a repost from the KDE subreddit. I can’t include links here so all links are removed)

I am trying out Fedora 40 in a VM. One thing I noticed is that Konsole is not displaying nerd fonts.

On Fedora 39 (i.e. KDE 5), font fallback just works. You just have to put nerd font in $HOME/.local/share/fonts and run fc-cache -f, then Konsole would display them.

Do I need to do something to enable font fallback on KDE 6 Konsole?

To reproduce:

  1. Download NerdFontsSymbolsOnly.tar.xz from ryanoasis/nerd-fonts (github), then unzip it and move it to $HOME/.local/share/fonts, then run fc-cache -f. Close all instances of Konsole afterwards
  2. Open a new instance of Konsole. Go to Nerd Font cheatsheet and search for a random nerd font symbol (e.g. nf-fa-fedora), then copy the Icon variant (not Class or UTF) and paste it to Konsole. Notice that it just displays a square.
  3. Go to Konsole settings, create a new profile that uses Symbol Nerd Font Mono as font. Then create a new Konsole window with this profile and paste the nerd font symbol again. The symbol is displayed correctly in this case.

This issue also happens on a brand new KDE Neon installation.
Also, I just tried Debian 12 (with KDE 5) on a VM and fallback font works out of the box.

Just discovered that this is not specific to Konsole: The plasma clipboard (press win+v to show) can display installed nerd fonts in KDE 5, but not in KDE 6.

I think this is a bug, but I don’t know which program is responsible for this.