Re: '34 years of development - Windows 10 is the result'(@ Patrician) (tl;dr)
"Linux, in any form is not a viable replacement for Windows as an OS"
Four years ago, I decided to do my best to never have to install a MS server again. Since then, I've installed -and maintain- about twenty of them. The happiest server owners you'll ever meet!
Regarding desktops, when one of them has to be taken behind the shed, but runs vintage software the company can't allow itself to rewrite/repurchase, there are several options, including virtual machines and dual boot+ heavy firewalling of the Windows installation, so as to access only, e.g. game servers or Autodesk's cloudy karp. Legality? You have a valid Windows license, you are in the clear.
Regarding hardware support, I've done this a few times to allow customers to use old stuff -big format scanners and plotters. For some of them there are open source drivers that can [communicate with]/[emulate] almost anything. In the worst case you can buy an ElCheapo Chinese comms board -Ej, SCSI or Serial interfaces. Agreed it can be a hit or miss thing, but those boards are nowadays so cheap that if one of them doesn't perform as expected you can either absorb the cost or send it back and buy a different one.
My point is that thanks to Linux, lots of people can keep using their old stuff, sometimes for decades. It takes a little bit of time and effort, but it usually ends up working well. Of course you don't do this for a cheap personal devices like A4 scanners or laser printers.
Sorry for this brick of a comment! 8^)
* In reality, its equivalence in the European national coins of that era.