They share a kernel, shells, package management as an application distribution model, and many disparately developed complex systems. They all run the same soft

They share a kernel, shells, package management as an application distribution model, and many disparately developed complex systems. They all run the same software more or less. Once you've used a few dozen different Linux distros, which I have over the 20 years I've used Linux for things, you find that almost all of them are basically the same. Occasionally there's an outlier like Gobolinux or Rox that everyone ignores but even they still has most software in common.