Linux Mint is a good choice but it doesn't come with a GNOME flavour by default. You can install it yourself if you want, though.

I moved to Fedora after leaving Ubuntu. Worked fine for me, but you'll have to re-train your muscle memory for some terminal commands. sudo apt install becomes sudo dnf install and rpm is a little different from dpkg. Other than that, with the Dash to Dock extension, Fedora feels exactly the same as Ubuntu to me.