@cis Most of your example fonts do not actually contain layers. In any case, sending around a layered font with TrueType layers as ttf file is a bit odd because that format does not support the such layers. The sfd file would be much more useful. Anyway, see
github.com/zauguin/COLR for some scripts to generate a color font based on fontforge layers. (Requires the fontforge python module, texlua and a (more or less POSIX compliant) shell)