For me it’s PeppermintOS.
I started my Linux adventure a few years ago, and haven’t owned a Windows PC since.
I currently use Arch on my main rig, and I wanted to install Linux on two old laptops that I found laying around in my house
I then remembered the first distro I ever used, which is PeppermintOS, and I was amazed at the latest updates they released.
They even have a mini ISO now to do a net-install with no bloat, with a Debian or Devuan base.
Sadly, I believe the founder passed away a few years ago, which is why I was really happy to see the continuation of this amazing project.
The nature of FOSS suggests (make that extra italic) that the most popular distros should be those that actually work the best. Totally agree that Ubuntu is an outlier, and even that is because of choices Canonical made – and corporate decisions really aren’t typically a part of FOSS.
That said, I truly enjoy smaller distros for hobbyism. I don’t necessarily see a use case where they should be chosen over a larger one, except for the really annoying fact that distros with corporate backing will always also tend to get quicker adoption.