There is a recent fork of elinks which includes basic gemini support https://github.com/rkd77/elinks
There is also w3m with inline image support. https://www.howtogeek.com/103574/how-to-browse-from-the-linu... https://github.com/tats/w3m
Using firefox or chromium as under the hood back-end headless (browsh+firefox) would of course be best, though not as lightweight
I was about ¾ of the way through that article and thinking "as an academic exercise, sure. otherwise this just looks like 'its been done a thousand times before... but not by me.'" which was leading me to share the page for elinks.
There is browsh but it's pretty slow compared to Lynx. I'm currently porting Chromium to the terminal with a text and a SIXEL back-end, I'll share it on HN next week (no Classic MacOS support!).
$ lynx --version
Lynx Version 2.8.9rel.1 (08 Jul 2018)
libwww-FM 2.14, SSL-MM 1.4.1, OpenSSL 3.0.7, ncurses 6.4.20221231