Thanks! While far more tedious than just being able to see HTML in a browser when going to a URL (expected behavior for the last 30 years), zygolophodon does seem like the least worst option. I've now installed it on my newer machines which have python 3.6. For older computers I guess I'll keep appending .rss to the user profile URL and and finding the relevant post by eye (or just ignore mastadon URLs).

Guessed the name was related ;-)

https://en.m.wikipedia.org/wiki/Zygolophodon