Indeed, xterm showed that it was missing libsdl-ttf, which the deb package had not forced me to install. I have installed it but still get an error related to the fonts:
X Error of failed request: BadName (named color or font does not exist)
Major opcode of failed request: 45 (X_OpenFont)
Serial number of failed request: 8
Current serial number in output stream: 10
I have tried copying /usr/share/fonts/truetype/msttcorefonts/ from the core, but no luck.