Hello,
I think I have understood the cause of the error.
In the official rinpy package, the fonts file are provided, (you can
find the in the repo[1]). In the debian package, the two files where
replaced by links to the font directory :
ls -l
lrwxrwxrwx 1 root root 60 5 avril 01:07 Roboto-Light.ttf ->
../../../../../fonts/truetype/roboto/hinted/Roboto-Light.ttf
lrwxrwxrwx 1 root root 62 5 avril 01:07 Roboto-Regular.ttf ->
../../../../../fonts/truetype/roboto/hinted/Roboto-Regular.ttf
But the link is wrong. The fonts are installed in
/usr/share/fonts/truetype/roboto/unhinted/RobotoTTF, and the links
points to /usr/share/fonts/truetype/roboto/hinted/RobotoTTF (missing
[un]hinted).
[1] https://github.com/renpy/renpy/tree/master/launcher/game/fonts
