In the past: Redhat, then Mostly Debian or Debian derivatives. Mepis was great for the time it was a thing (2003 - 2005). Also Gentoo for awhile.

Nowdays: Arch and Fedora mostly. I put Fedora on a laptop a couple of years ago while trying to see what would work with it and I have been extremely surprised by it. Packages are really up to date, I have gone through a major revision upgrade with no problem at all. Arch is great, but you have to pay attention and deal with change. Fedora is just as up to date but I don’t have to manage the changes.

And Fedora recently added KDE as an official release instead of a “spin” which is all the better. I hope they keep going, I read that they are not a big team and one of them just left.