Windows (Client) and Linux (Server) in the company.
MacOS (Laptop) and Linux (Server) at home.

Windows Vista!

Windows 10 Host and Ubuntu Jammy Jellyfish guest. Can't go wrong with that setup any day!

Window 10 on both laptop and PC. I can say that by far this is the best OC that can be found online, yes we have Linux, but for me this OC is like a deep forest with a lot of wild animals, i know nothing about this OC. Even with minor problems, like for example Windows activating kms activator sometimes lagging, but it can be solved. I still think that Windows is the best OC by far, so i gladly use it

Ubuntu mostly, Windows 10 for specific softwares and games, Win 10 LTSC minimal for terrible netbook

Windows 11 Destop, Windows 10 laptop.