I got it working! Thanks for your help! The trick for me was running the game in bordered windowless mode with linear scaling after editing fonts.json with a font contained in fontlist.txt.
For anyone who is interested in my fonts.json file:
{
"fontblending" : true,
"fontwidth" : 20,
"fontheight" : 32,
"fontsize" : 32,
"typeface" : "Ubuntu Mono",
"map_fontwidth" : 20,
"map_fontheight" : 32,
"map_fontsize" : 32,
"map_typeface" : "Ubuntu Mono",
"overmap_fontwidth" : 20,
"overmap_fontheight" : 32,
"overmap_fontsize" : 32,
"overmap_typeface" : "Ubuntu Mono"
}