Fonts installed in symbolic linked folder are lost in flatpak

[Jehan]

Someone noticed that some fonts were missing in GIMP.
For instance on a Fedora, if you install the package texlive-tex-gyre, it would install a bunch of fonts under /usr/share/texlive/texmf-dist/fonts/opentype/public/tex-gyre/ and add a symlink to this folder under /usr/share/fonts/.

Now I can note that the freedesktop runtime adds /etc/fonts/conf.d/50-flatpak.conf and in particular that /run/host/fonts is mapped to /usr/share/fonts/.
Unfortunately while doing so, it doesn't take into account symlinks which are not remapped. Hence any fonts which are installed as symlinks on the host system (such as this Tex Gyre package) are lost in the sandbox.

Of course, special-casing these would work, but this is obviously not very good. A generic solution is needed.
Could something be done about this?
Cf. flathub/org.gimp.GIMP#20

[TingPing]

This is handled by Flatpak not the runtime: https://github.com/flatpak/flatpak

[Jehan]

Ok. New report: flatpak/flatpak#2134