Note, TenFourFox isn't quite "modern Firefox", it's a fork of an old version with backported fixes and improvements. And on Snow Leopard (which only supports Intel), you'd want to use Arctic Fox instead: https://github.com/wicknix/Arctic-Fox.
> To your point, there are plenty newer MacOS versions that might still suit ones taste, still run 32 bit apps, and still get patched.
Where "plenty" equals "two", sure. Apple releases security patches for the last three Mac releases. So, High Sierra has one year left, and Mojave has two years.
> To your point, there are plenty newer MacOS versions that might still suit ones taste, still run 32 bit apps, and still get patched.
Where "plenty" equals "two", sure. Apple releases security patches for the last three Mac releases. So, High Sierra has one year left, and Mojave has two years.