Inter is one of my favorite sans-serif typefaces. Here is what I found to be missing:

Stylistic set 4 provides a small sharp s (U+00DF ß) based on the round s and a small l with a finial.

For consistency, I would like to suggest a glyph for U+1E9E ẞ that is based on the capital S instead of the tailed Z.

You may also want to provide a glyph for U+02AA ʪ based on the finial-l form (so that the joining looks more elegant; see, e.g., Fira Sans).