Yes, within Linux there is diversity -- I was not talking about that. The server space in 2026 is dominated by Linux.

Solaris ? Gone* WindowsNT ? Niche. HP-UX ? Gone* AIX ? Gone* macOS ? Not in server. FreeBSD ? Niche (smaller than WindowsNT though).

In another world there would be at least two open source server os-es battling it out (like in hardware where we have aarch64 vs x64 and so on).

(*) "Gone" means probably a rounding error by now.