I don't like solving things with regulation, because that's always a victory in one battle making the enemy stronger for all the following ones.
But doing this EU-style, like browser choice, only with operating systems, can be a solution.
People love cheap and easy things. That's how social media won over normal web. Seeing the choice between "install Fedora for freeeeeee" and "install Windows for 20$" significant amount will choose the former.