It is my understanding that the fonts from the system are shared to the flatpak environment, so i was expecting that fontconfig would behave the same inside than outside, but it does not.
In my system
tsdgeos@xps:~:$ fc-match Helvetica
NimbusSans-Regular.otf: “Nimbus Sans” “Regular”
In flatpak
tsdgeos@xps:~:$ flatpak run --command=sh --devel org.kde.okular
tsdgeos@xps:~:$ fc-match Helvetica
LiberationSans-Regular.ttf: “Liberation Sans” “Regular”
NimbusSans-Regular.otf is available in flatpak too though
tsdgeos@xps:~:$ fc-cat | grep NimbusSans-Regular.otf
“NimbusSans-Regular.otf” 0 “Nimbus Sans:familylang=en:style=Regular:stylelang=en:…”
Any idea why that would happen?