Someone on the newsgroup comp.infosystems.gopher mentioned that Gopher type "I" (and probably "g") are not supported and give the error message Unknown gopher selector.
He said, he was surprised because type "I" is a canoncial type from the original Gopher RFC 1436.
Maybe you could implement the types "I" and "g" like images on gemini (first download, then open in configured application)?