The other comment here about how it's like complaining it does not work in IE6 is really pertinent: Yes it damn well should, because I should not need the latest technology just to do something that would've been perfectly possible with the technology of TWO DECADES AGO. It should be entirely possible to use GitHub with a text-based browser because none of its interactions require anything more than that.
It's sad that I could probably write a more accessible interface in less time and resources, and I haven't even done much in the way of web development, yet dedicated web-developers with uninhibited trendchasing mentality will fuck it up so badly with this constant need for useless breaking changes.
Seriously, fuck this "modern" bullshit.
https://news.ycombinator.com/item?id=23136688
Would it be possible to make a form with all those features and that works (at least with 95% of the features) with your legacy (dead) browser of choice, be it IE6 or Pale Moon? Sure, it would. But to do that, GitHub would need to spend a lot of resources, even though most GitHub users do not need those dead browsers. Those browsers don’t support many modern APIs that web apps need, or that make developers’ lives easier.
Speaking of dead software, Pale Moon dropped support for Windows XP in 2016 [2]. What happened? Why does software drop support for old runtime environments? Because nobody has the time and resources to test things on XP, and to write polyfills for features that XP does not support, or to skip some features because they don’t want XP users to get a worse browser, and because new features can make your software better for the user or more secure.
The world has moved on. Install a modern version of Firefox (or Chrome/ium if you must) and stop complaining.
[1]: https://caniuse.com/?search=components
[2]: https://en.wikipedia.org/wiki/Pale_Moon_(web_browser)#Releas...