Not Linux
I first used Linux when I was 13-14. Like many nerdy teens, I went through a cavalcade of distros: Red Hat, Fedora Core (2), Slackware, Debian, SUSE, Gentoo, Ubuntu, Arch. I’m probably missing one or two.
But there was another. Not Linux. FreeBSD.
The BSDs are weird. They’re older than Linux. They are closer to UNIX than is Linux. They have much the same userland as Linux. But they are decidedly not Linux.
I first tried FreeBSD around 2004. I had a brand-new Athlon64 3200+. Windows didn’t have a 64-bit version yet, and I was itching to take advantage of the extra bits (not understanding they didn’t mean much for performance). Enter FreeBSD.
It was actually a failure, thanks (of course) to driver issues. A generous (not to mention patient) user on Freenode spent hours teaching me how to build a new kernel. That was my first introduction to vi (not vim; the default FreeBSD install didn’t and still doesn’t come with something as new as a 1991 text editor). And after hours of work, we learned that the FreeBSD Radeon drivers just didn’t compile on amd64, so I couldn’t have hardware acceleration. I wiped the install.
(Looking back, I don’t know why this was so important to me. It might have just been the principle of the matter.)
Spoiler: I came back.
I’m not here to convince you to install FreeBSD, so I’ll just say this: FreeBSD, like OpenBSD, NetBSD, etc. is very much an operating system, not a distro, and that shows itself in subtle ways. Look no further than the handbook to see what I mean.