Some time before Ubuntu Hardy Heron (8.04), so somewhere around 2006-2007. Had a spare laptop I had installed (unsuccessfully) Gentoo on, then played around with stuff like Mandriva and Debian, and early versions of Fedora and OpenSuse. I’m a developer now, using Pop right now. Honestly I don’t really care which one as long as my tools and hardware work, and it works well enough on Pop.