Throughout history the overwhelming majority of unix-like software was designed to work only on the particular flavor of unix used by its author.

So exactly eves “Unix like software” will kids be missing that prevents them from learning about computers?

The overwhelming majority of UNIX-like software is available in the package managers right now for major BSDs.

I ask for a specific example, and you respond with more generalities.

Aside from the BSD software, the Mac software, and all the software that’s actually POSIX-compliant (on purpose or by accident).