As insane as it sounds, Albania is actually a member of NATO. Serbia is not.
Hence an attack against Kosovo by Serbia will be the equivalent of Russia invading Ukraine.
World War three!
I think it’s more fundamental than that, they just don’t like Serbia. But I don’t think it’s the equivalent of Russia invading Ukraine, because Serbia is a tiny country, with less than 23k active duty and no nukes.
Kosovo is not part of Albania. Kosovo is not a member of NATO.