If you go back 15 years, to January 2010, you find x86-64 hardware that you could install modern Linux on as easily as running the installer off a USB stick. The unibody 2009 MacBook Pro was out by then, so your computer could even look totally normal at a Starbuck’s today (and connect to the WiFi just fine). That machine will take 8 GB of RAM and run the COSMIC desktop written in Rust for Wayland (run it well-I have done it).

Go back another 15 years to 1995 and you have Pentium desktops. Linux was created just a few years earlier for similar but even more modest hardware (as was Windows NT). Not every modern Linux distro will still run on Pentiums but many will. You may have to burn a CD but up-to-date Antix, Q4OS, or Adelie releases will still work out of the box. Certainly NetBSD will. Not everything will still run on 32 bit machines and RAM is going to be a problem. The “modern web” would bring those machines to their knees. Still, surprisingly modern.

Go back another 15 to January 1980 and you have to wait almost two years for hardware that will even run ELKS. Crazy.