Desktop computers are the one and only one space where Linux doesn't utterly dominate as the kernel of choice. Supercomputers, servers, embedded devices, basically all Linux. In the mobile space, Apple and Android are a duopoly, Microsoft repeatedly tried and failed to enter that market. Microsoft managed to secure a de facto monopoly on the desktop, kept Macintosh like a pet to ward off actual monopoly lawsuits, and has spent the last 20 years just making their product worse for the user in order to wring another pint of blood out of the same moldy old turnip.