> For some earlier versions of macOS, Safari might also be available separately from the Updates tab of the App Store.
Is that a message Github have put out, or have they accidently rolled out a new feature that has a bug in Safari 12? That seems more likely to me. Github's browser support is usually very good, and it'd be incredibly disappointing if they've broken something intentionally.
Best guess: they removed a polyfill somewhere.
You don't; Safari 13 runs on macOS Mojave (and macOS High Sierra, if you're still using that).
I do (I won't upgrade past High Sierra on an older iMac as it breaks text rendering on it's non-retina screen so badly).
https://www.howtogeek.com/358596/how-to-fix-blurry-fonts-on-...
at this point, i don't think you even have to do that terminal thing anymore; you can just enable it in settings.
You also have to disable and re-enable it during the Catalina install or it really messes things up.
I can understand not developing new features for Safari 12, but speaking of regressions, why would you go break things that used to work a week ago?