Redhat 4 - Kernel 2.6
Man, that was a long time ago
Things have changed a lot for Linux since then.

Redhat 95 was my first install. I think it was kernel 1.2x.

Now I rum Linus Mint Cinnamon 18.3 I have not tried anything else

In 1996 paid $25 for a box containing 6 CDROMs that contained "everything Linux" that existed at the time including several 1.2 kernel distros along with all the applications that existed at the time. Back then 56k dial up modems were still the main residential access to the Internet. I even partitioned my 120MB (that's megabytes) hard disk with 4 primary partitions to boot MS-DOS/Windows on one, OS/2 on another, Windows 95 on the third and trying out various Linux distros on the fourth partition. All done on a 486 PC with 4 MB of RAM. Yeah the good old days!

SLS 0.93.1 on a couple dozen floppies. I ran it on a Packard Bell 286. Ubuntu 7.04 was the first version I used when I switched to Linux as my primary OS.

A colleague showed me an install of 0.12 in the early 1990s. I was smitten.
Brought it up on a 386, never looked back

Yeah, you and me both!

Yggdrasil with the 0.99 kernel was the earliest version I used (1994), but technically, I tried Red Hat with the 1.0X kernel first.

Well my vote 2.4 was just a guess. Slackware from the mid 1990's. I never got much of the GUI running perfectly and migrated to SUSE and then Ubuntu 5.4. I confess I have no idea what Debian kernel 5.4 was running. Ubuntu was the first system that actually seemed totally functional (at least for my level of need).

Got three 3.5" floppy disks from a student working part time at the company I was with at the time, which has Linux v0.12 on it... ;-)
That's almost 27 years ago now...

I have no idea...
but it was RedHat 6.0
Wiki says kernel 2.2.5-15
We'll go with that.

I was a graduate teaching assistant when I first used Linux back in 1999. I had grown tired of the dreaded "Blue Screen of Death," but just did not like the Mac interface, and so, I was determined to try something new. My first two versions were Red Hat Linux 5.0 [Linux kernel version 2.0.32-2], and Corel Linux [Linux kernel version 2.2.16], which had WordPerfect 8, which I liked at the time.

This Linux dual-boot proved effective for me, as I could continue to work as I went about solving office software loading issues in Red Hat and networking issues in Corel. Sadly, they discontinued Corel back in 2000, and I didn't like StarOffice that well, but except for a brief sojourn with Mandrake, I stuck with Red Hat through versions 6.x [Linux kernel version 2.2.5-15] and 7.x [including 7.2, with Linux kernel version 2.4.2-2] until 2006, when I shifted to SuSE 10 [Linux kernel version 2.6.16]. Nowadays, though I still have some openSUSE boxes, I prefer Ubuntu and its derivatives [Linux kernel version 4.17], because that distro group puts up-to-date software on 15-20-year-old boxes that even the Luddites who work with me can figure out how to use. 8-)

A couple of weekends ago, a friend and I had to press a dozen circa 2000 boxes out of mothballs into service over a four-day marathon productivity session. After updating the software, those old boxes did the same amount of work--at the same speed as another unit with twice the number of new Windows 10 boxes--but without the issues.

I'm only a user, not a programmer. But I can testify that the Linux kernel is one robust powerhouse! ;-)

Redhat version 5, then Mandrake, then Debian since then starting with Potato, with kernel version 2.0.38.

Fedora Core was my first personal linux flavour, but prior to that I had been working on various flavours of UNIX from AT&T running LanMan servers under unix, Sperry, Spectrix, Bell Data (DT1?) for work.

Bit late in the game starting with Slackware 8.1 running the 2.4.18 kernel.

My first recorded Linux kernel version is 'Linux Red Hat 9 GPL kernel version 2.4.20-6', pre-installed on a Pogo Linux Altura in 2003 (now running Debian 9). I began using remote Unix-based mainframes (at Kirtland AFB NM, I think) to send batch Fortran jobs to a Cray 1 in the mid 1970s.