Im currently working on an uppercase font and the process is mostly straight forward but the integration of letter ß (Eszett) is i a major problem. There is an uppercase version and a lovercase version for this glyph (ẞ ß) but they are not linked inside Fontself resulting in either a Font with a missing characters or a font with fallback letters for all lowercase versions of the Latin alphabet.
Is there a workaround for this issue? Last time this topic came up was in 2019 and there was no clear solution: Uppercase font showing fallback font in illustrator
This seems like bug in the automated substitution process of Fontself. Using the uppercase version of ẞ should automatically create the same lowercase version.