German sharp s problem

[NDPtype]

The font doesn't have a small cap sharp s when I turn on the smcp feature:

It would be more correct if the sharp s is substituted with a "double s" when smcp is activated:

Can you please fix this?

[tiroj]

The double–S remains the standard German orthographic rule for case mapping of ß. If you want the smallcap glyph that corresponds to the uppercase ẞ character that was only recently officially recognised as an alternative case mapping, then you need to use that uppercase character (U+1E9E) and apply the c2sc rather than smcp feature.