My second distro was Debian 8, initially with LXDE (which has barely changed at all since then, so it's still nostalgic) then later switching to KDE Plasma 4. I probably hold the most nostalgia for it, even more than I do for my first distro (Linux Mint 17). For a while I was into Plasma Netbook, which I find to be an especially weird, nostalgic product of its time, and the Oxygen theme in general is probably my favorite default look for any DE.

I have fond memories of Kubuntu Feisty Fawn and the whole suite of KDE apps that were around back then. It's nice to see that Amarok got a new release recently after such a long time.

If you want to experience travelling back in time with an operating system then OpenBSD feels like a time capsule, albeit one which is still being maintained. I realise it is not linux but using it is very similar to what linux was like before 2010.

Slackware 7

Kubuntu 8.04.

It was the last release with KDE 3 and very polished for its time. Many applications from back then have vanished by now. Kopete was Magic, supporting all IM protocols (Including Yahoo video calls!), Amarok was so reliable and sleek.

Of course most things have improved since then, but I remember it fondly.

• ZenWalk was unique and great about 15 years ago as an easy Slackware with minimalist install.
• Chakra Linux was an Arch+KDEmod distro that kind of went away.
• Bodhi Linux has its own desktop called Moksha.
• There is a GNUstep Live CD that comes out every few years, based on Debian. It is a unique setup from a time when the future of computing was promising. I think it is distributed on LinuxQuestions or some other forum.
• There was a distro called gOS about 15 years ago that used a lot of desktop widgets and Google apps. Their business model was basically, "We are going to re-skin Ubuntu and call it gOS and hope Google buys us." It did not work out.
• Darwin was upstream for macOS and for many years, there was a community of users who would port the traditional *NIX stack to it. Xorg, traditional window managers, a ports system, etc.
• Frugalware Linux was well polished and kind of a spiritual successor to Zenwalk.
• openSUSE 10.3 had the most beautiful Gnome setup. It was unique in that it had a single panel, a modified Clearlooks theme, and a Vista-style start menu.
• OpenSolaris likewise had a very unique and beautiful look, with its macOS-inspired Nimbus theme. I think this was the best looking theme of that era.
• SimplyMEPIS was my first Linux on a T61. I had used FreeBSD for the decade prior. I don't know what was better about SimplyMEPIS than Debian, nor do I know what SimplyMEPIS meant versus regular MEPIS. It's kind of like Claws Mail and Sylpheed Claws. Some times we just throw words together and give it an icon and there it is.

I used all of these at some point.

RedHat.

Not Fedora. Not RHEL. Back when it was just RedHat Linux.

Lubuntu with LXDE

Idk about nostalgic but north korea makes their own linux distro, that's gotta rank high on the interesting list

Lindows

Ubuntu ca 2010

Play some Nibbles from that era

Nostalgic doesn't necessarily correlate to "special place", so It Depends™.