need to have an understanding of operating systems, so they can think about alternatives
need to be aware of the actual alternative
need to be willing to learn something new
need to be willing to leave some applications or games behind
need to choose a Linux distribution
need the technical ability and understanding to actually download, flash and boot from boot system, install it and setup initial, such as root password and such
These are basic and trivial stuff for us, but most normies don’t have this understanding and interest to go this far. And then it depends if they are happy and stay. Even if every PC manufacturer and distributor would offere the same PC with Windows and Linux, most would just choose Windows (probably). This is the current reality.