I've been trying to improve unicode support recently in my theme's fonts, however I've run into an issue with convttf not reading and converting icons in a font past a certain unicode number. Based on some quick tests, it appears convttf reads up to 5 number unicode and stops (U+XXXX is read while U+XXXXX isn't) Seems it's able to read
plane 0 while plane 1 onwards cannot be read. This covers a good chunk of modern emoji, certain mathmatical symbols (𝔞𝔟𝔠𝔡, 𝘢𝘣𝘤𝘥 etc) These aren't uncommon in songs, I've gotten a few requests to add them, is there any way I can force convttf to use these further ranges or will the script itself need to be changed?