I have not heard of Gemini before, but I tried the SSH that was linked above, and read about it. It seems a interesting idea. I don't like insisting on TLS either; I think that perhaps better would be like with HTTP, where the URI scheme is different for TLS or plain, perhaps "pgemini://" for the plain variant (the only difference, other than that there is no TLS, is that the 6x response codes are not supported).