Go to your appearance settings and look at the wallpapers. Found the 8.04 wallpaper Easter Egg?
Around two months ago in March, the Ubuntu community held their wallpaper contest, the 2020 Desktop World Cup. The finals of 19.04 Disco Dingo and 8.04 Hardy Heron came very close-49.9% to 50.1%.
To celebrate, the Ubuntu team(s) added the 8.04 wallpaper to the release.
So although Ubuntu Cinnamon 20.04 has been released, if you want to, download the Ubuntu Cinnamon-colorized wallpaper and set it as your background to have some fun, if you want the old Jazzy stile of classic Ubuntu.