If you look at the map, only areas covered by 400mi radar from NATO or neutral airspace are Kherson, Crimea, parts of Zaporozhye and Chernigov region. Donbass is out of range. I doubt that Ukraine will get their own AWACS or that NATO planes will enter Ukraine's airspace.
AWACS is superior to ground radars, but only if you are able to protect it from enemy fighters.
By Russia, in Ukraine, to track low-profile targets and direct interceptors (since Russian AWACS doesn't have datalink, directions were given by voice over radio, lol). Also, by both sides for reconnaissance purposes, since AWACS can detect ground and naval targets, too.
It's just a flying radar, so everything that works against regular radars would work against it (except going low).