Update: the newly installed font shows up in listTrueTypeFonts, but, as an example, when I install "Courier New", I get an error message when trying to use it:
Error using insertText>populateGlyphBuffer_sim
FreeType: Unable to load font file.
Error in insertText (line 146)
populateGlyphBuffer_sim(font,fontFileName,faceIndex,fontSize);
The crash happens in visionPopulateGlyphBuffer, which is "an undocumented builtin function" according to Matlab help.