I don't see this as the Windows being default on a laptop problem. It is a problem of letting companies grow too big. Google equally abuses their position with Android. We need to force big tech into splitting. No way around it.

Adtech, IT infrastructure, operating system development, office software and browser development should never belong to the same business. It is not Windows on the laptops that makes Microsoft at the center of IT, it is all the software ecosystem around it which Microsoft also owns a huge slice of it. Throughout the 90s and 00s they were let to buy all of their competition that released software on various platforms. Everything from finance software, reporting software, Microsoft Office suite, Azure Active Directory all belongs to Microsoft. There is no competing with such behemoths. They are guaranteed to be abusive.

Breaking this kind of monopoly first requires encouraging open standards. Got a government contract? You have to release every single detail of the output formats with all the features you support on them. Delivery of all sorts of software to public institutions can only be made with the full copyright assignment to public as well.

This doesn't absolve Linux or any other third party OS developers from being competitive. Linux currently isn't competitive. It is 2 decades behind in many areas. However, a fair market economy will actively break behemoths like Microsoft and let other developers to compete with them. It should encourage actual competition and prevent cheap buyouts of competitive products.

Similarly enforcing ownership rights is critical. If you cannot change software on a device you have, you don't own it. In a properly competitive environment you don't need the knowledge to install OSes. A competitive business would handle that for you or other smaller businesses providing such IT support would also pop up.