Some laptop manufacturers (and at least one of the larger ones) already offer Linux (Ubuntu) as a pre-installed OS. I suspect this will become more common if/when Linux becomes more popular as a mainstream desktop OS. Most likely it will still be 1 or 2 pre-selected distros though even then.
It’s a good question but I honestly have no idea how that works even today with windows actually because I have not owned a laptop in 15 years. In my mind, the laptop manufacturer has to guarantee compatibility with any OS it provides but even then, some support from the OS side may be needed. The best way to handle that would be if the manufacturer started contributing to the Linux kernel and provide full driver support because then everybody wins in the long run.