Does anybody remember Minix?
Around 1981, working with PDP-11 (Q-Bus) systems, RT11, TSX,
I encountered Integrayed Solutions Inc (ISI) Unix systems, 68010
and then worked with SCO Xenix on PDP-11 and PC systems.
Minix was an 8086 or 8088 teaching O/S. 8086 small model. ie.
64Kb programs and data. When Linus Travalias ported this to the 80386 in small model,
small model being 4Gb, The whole Open Source OS scene opened up!!!
My first distribution was OpenSUSE. Then I switched to Arch Linux, then to Fedora. 
Hello. Mine was Slackware, eons ago. I tried it because I read somewhere that DOOM played faster than in DOS. And it did!
I remember playing Unreal Tournament under Linux about 20 years back. So definitely performance wise much better than under Windows XP
Hi
My first distro was fedora, it was very nice about 2001 year
Slackware pre 1.0 (pre 1.0 Kernel) on a 486
UNIX, ATT 3B1(with Internet/SLIRP/UUCP)
Leading up to UNIX
OS-9(not really UNIX) on a TRS-80/CoCo
Vax/VMS
MITS/Altair(1st exposure to MicroSoft via BASIC)
Today primary Rocky9, used Debian, Ubuntu, Slackware,Fedora, RHEL, CentOS, Redhat Pre-RHEL
Other Work related
SGI/Irix
BSD
Solaris/SunOS
Data General/ Aviion
Harris Night Hawk
DEC/ ULTRIX
Great post, dear Ian!
My first distro was Slackware circa 1997/98. I must have run it exclusively until I switched to debian around the year 2005. I had used debian as my daily driver off/on (because I was/am a mac user also) until 2019 ish? Where I switched to fedora and later on fedora & rocky
As per systems I have used as a systems admin,
windows (obv)
HP UX
AIX
FreeBSD
CentOS
RedHat
Debian
And now I’m hoping we can migrate our aging centos servers to rocky <3
1990 - Prime Computer EXL 300 – running AT&T System V.4. The concept of a “distro” was not concieved yet. Also BSD Unix running on MIPS R3000 RISC systems (shortly before it became an SGI subsidiary). These were the days when “grep” seemed like magic. Then in 1993, SunOS, then Solaris, then RedHat and Fedora. Present day, CentOS moving to ROCKY!
Some time ago I described my journey from a Commodore VC-20 back in 1983 up to Rocky Linux on my workstation in a blog post:
My first distro was SLS, in 1993 I think, when I was running a BBS for the iCE art group, called The Pantheon. I switched to Slackware pretty quickly afterwords when I found I could run the BBS in a DOS emulator. We had a grand plan to bring ANSi art to Linux 
Switched to Redhat in 1996, and then Fedora which I still run to this day.
Ubuntu 9.04 Jaunty Jackalope. Compared to others here, I am relatively new to Linux.
My first distro was Yggdrasil Linux back in 1996(?). I was a summer intern and remember using kernel 1.1.x and often compiling in the latest Intel e100 driver.
Later we moved to Slackware and then Red Hat Linux (around v6?). Eventually things moved to RHEL-based distros.
I ran Ubuntu 5.04 (2005), but that was just for fun. My first attempt at running it as a daily driver would have been Fedora 8.
From my perspective, from a commercial standpoint, the first Linux version I deployed was RedHat Desktop in 2001. I played with an earlier release at home, but for a company, it was that.
RHL 7.1 (Seawolf) - April 2001 Released
I was a DOS guy from the 70’s where there was no such thing as directories, I did my first Windows release in 1984 at a Newspaper in Savannah GA. I played with DEC VAX, IBM MVS, PC/MS DOS, Windows XXX, Apple2, Macs, CICS, Apollo Unix, Solaris, AIX, HP-UX. Up until I got involved with Cacti, I was pretty much a Windows guy. Not so much any more. Linux or bust!
It’s not clear to me if we started in the Unix world before Linux existed if that counts as making the switch?
Anyway my first *nix exposure was Unix System V R4 on an NCR Tower in 1984.
The SunOS, then Solaris.
My first Linux would have been at work around 1995, and to be honest I can’t remember what it was. Redhat? Debian? Slackware? But I didn’t install that I just ran whatever it was that someone else had installed for me.
And then a new job and back on Solaris. But then after that, RedHat and CentOS. And Rocky of late.
But this was all through work.
At home, I was Mac, and then Hackintosh for many years, until finally Apple did too much damage to MacOS such that it was no longer recognizable and useful as a type of *nix. So I installed Manjaro on a new laptop about three years ago. That was actually the first distro I chose, and installed, and ran, entirely on my own. I wanted something that was different from what I was doing at work.
And now I’m looking for a new home distro with a package management that doesn’t break all the time (like Pacman does). Leaning towards going with something that is more familiar from work, either Fedora or Rocky. But maybe I’ll be more adventurous.
I’ve been bitten by Pacman in the past, most recently with Cachyos although I did manage to recover it. I’ve been running Fedora on my laptop for the last few years upgrading every six months or so. My home desktop also (built 2018), with Fedora which I use mostly with Steam for gaming on an Nvidia 5050. Rocky usually I’m using for servers, be it a VPS or bare metal.
Slackware 1.x. I ran a personal web, and e-mail server with 2MB RAM in the early 90s. Back then I was using HP-UX, AIX and the like at work.
I started experimenting with Linux very early 2000s, I want to say it was Knoppix, Mandriva, Debian and probably something more. Didn’t really stick though.
It wasn’t until I found Gentoo around 2004/2005 that I really got into Linux. Have pretty much been running it privately since then, with periods here and there of off time. I have tried other distros for desktop, but I always revert back to Gentoo. It fits me perfectly and is what I’m most comfortable with. Running it with systemd today, but been a long time OpenRC user before.
In homelab I run a proxmox with a TrueNAS, a Rocky and a bunch of FCOS. There’s also a baremetal Rocky around, acting as a backup server. For work it’s pretty much exclusively Rocky, with some FCOS sprinkled in here and there.