For me, it was Mandrake, I think it was back around 2000. I played so much Tux Racer on that machine. However, after they switched the branding to Mandriva, the OS started to run pretty poorly for me around that time. I stayed away from Linux entirely until around 10 years ago when I friend introduced me to Mint. It's been my main ever since, though I've played with others since then, like OpenSUSE, Ubuntu, and most recently, Debian and EndeavourOS.