My first linux was Winlinux, which installed in windows 98 as a program. You would load it like any other windows program, and it went into a full Linux desktop OS that was very primitive back then. It was a very old version of KDE. Then i tried Red Hat 5.2 Deluxe, which i still have the original manufacturer CDs for. Then i moved to Mandrake 7 and went on up from there.
Redhat. Many years ago. Had a horrible time getting it to install on a noname laptop. Thankfully as the years went by my experiences installing Linux got much better and the last few years have been buttery smooth.
Apparently that was based on a 2.4 kernel - but back then it could have been a walnut for all I knew...
Setting up dial up was difficult enough, trying to get a USB DSL modem to work was eye watering...
I particularly remember the Mandrake GUI tools being extremely flakey. I didn't know about mailing lists or the few forums that existed back then (I'd only been using the net on metered dial up for less than a year (but computers for much longer - late '80s) so I just went out and bought a few books and struggled on - mostly breaking stuff and reinstalling.
Nowadays we have it easy (perhaps too easy). Forums like this one are a great, free, resource, populated by volunteers. It's a pity that some people don't really get this and often you see the type of member who turns up with an attitude where they feel it's ok to demand help and behave as if they are dealing with paid customer support people and thus believe they don't need to put in any effort for themselves.
I don't remember if the first was Red Hat or Mandrake, but I ended up using SUSE (no cost SUSE, before the OpenSUSE fork, iirc) when I set up a personal computational system, back near when AMD first released the Opteron.
I started with Fedora and then migrated to Red Hat. This was before RHEL. I use CentOS at home and Suse at work.
Knoppix or any of the live CD distros are an excellent way for beginners to start out on Linux. Im not a big fan of Unbuntu because it reminds me too much of Windoze