Software engineering in Canada in the 2000s. Most of the labs in my university ran Linux, at least in the engineering, math, and science areas of campus.

Personally I ran, depending on the year, LFS (Linux from Scratch), Slackware, or Gentoo (which still lives on that laptop today but also it hasn't been booted or connected to a network in like 10 years).

I think there was only one lab with Windows. We also had a lab of Solaris machines but I bet those are gone now.

No idea what Law, Nursing, and other faculties in the other side of campus used.