While still not an official flavor, Ubuntu Unity 21.04 is based on the Ubuntu 21.04 (Hirsute Hippo) release, which means that it ships with all of its internals, including the Linux 5.11 kernel for better hardware support, as well as the updated toolchain consisting of GNU C Library 2.33, GCC 10.3, GNU Binutils 2.36.1, LLVM 12, and Python 3.9.4.
But Ubuntu Unity 21.04 is here to give fans of the good old Unity 7 desktop environment a much-improved experience by shipping with a new Yaru-Unity7 theme that features a transparent launcher icon, a new Plymouth boot loader screen theme, as well as new wallpapers based on the Hirsute Hippo mascot.