Flatpak Square box for text - How to fix

Error

Text is displayed as 'square' boxes, instead of the usual text.

Solution

flatpak run --command=fc-cache x.xxx.Xxx -f -v

x.xxx.Xxx is an example. Replace this with the application name seen on flatpak list.

Example

flatpak run --command=fc-cache org.darktable.Darktable -f -v