What is "vanilla Linux"? Ubuntu+Gnome, Mint+Cinnamon, Fedora+KDE, Arch+COSMIC ..?

Each distro, platform and desktop manager and related apps are relatively different, though all work pretty well on modern hardware. I'm currently running PopOS COSMIC alpha with the 6.16-4 kernel via mainline. It's been pretty good, though there have been many rough edges regarding keyboard navigation/support in the new apps.