Strangely (or not) there's a #Gemini client for the old Amiga (AmiGemini) but not for Mac OS Classic (?)
Thankfully the #smolnet proxy at http://portal.mozz.us also works with insecure http. So here I am on the GeminiSpace from a Mac Mini running Mac OS 9 in Internet Explorer 5. I tried Netscape but there's an issue with new lines on Antenna and other capsules.
Using custom fonts & colors it's visually pleasant on 1280x1024 screen and quite snappy.