Check the lfftools GitHub repository, join the #retroprinting channel on Libera.Chat, and always keep a copy of ttf2lff in your toolchain.
TrueType Fonts (TTF), by contrast, are "shape-based." They define the outline of a letter. On a screen, the computer fills that outline with pixels. In a CAD drawing, a TTF letter is actually a complex "hatch" made of polylines. ttf2lff