Unfortunately, there’s no way to get energy out of waste heat that won’t be spent pushing that heat a little harder. Already a significant amount of energy is spent cooling data centers, any attempts at energy recapture will just make that cooling harder.
The best we can do is something like district heating, because heat pumps can get over 100% effective efficiency.
I’ll believe it when I see it. They have so many material science challenges ahead of them and aren’t very forthcoming with progress.