Looks like Spartan is already supported by the excellent Lagrange [1] Gopher/Gemini browser from v1.13 onwards, so I'm happy to discover this! Thanks for sharing!
The cool thing about something like Spartan is that you could implement a browser on a microcontroller. HTML would be a lost cause. Imagine something like an ESP32 with a touch-screen. You could create a complete browsing device for less than 25 quid, say. Likewise for gopher.
If I may be permitted a small plug, I have a forked version of the bombadillo browser here: https://gitlab.com/mcturra2000/bombadillo You can use it on a terminal. It allows you to browse Spartan, which the original does not. It also allows a printing facility, so that you can pipe output to another process.