So, it appears that I’ve (accidentally?) written a Mastodon client! It’s been public for long enough that I probably ought to write about it.
Brutaldon is a brutalist (mostly) web client for Mastodon and Pleroma. You can use it to connect to most instances from almost any web browser — I commonly use it from Lynx and w3m, as well as my day-to-day Firefox, and I’ve seen others use it on retro browsers on 1990s and early 2000s hardware.