I think that windows is still the biggest but is changing very quickly to linux, for normal office work and a home computer that is used mostly for surfing and doing spreadsheets and documents, you can even use a raspberry pi running Debian without a problem. And Pi4 is much cheaper. (You can even use Ubuntu on Pi4).
I personally have to use windows 10, as my development tools are all currently only for windows. I had to move to Windows 10 as I had to upgrade my hardware and all new hardware only comes with windows 10 drivers (Windows 10 is the worst windows since windows ME).