I kept getting this annoying message when starting mythtv-setup on my QNAP:

MythFontProperties: Failed to load 'Liberation Sans', got 'FreeSans' instead


Turns out the Liberation Sans font is a freely available one, I downloaded mine from here

I then installed the ttf files into /opt/share/mythtv/fonts, restarted mythtv-setup and no more warnings about the fonts.