It will require some involvement of state, but it is plausible, that critical infrastructure will be required to have this covered and certain big, licensed private contractors may be able to operate air defense systems on such sites (do you smell the money and lobbying effort?).

Also this may influence the design of such data centers. A drone that a paramilitary group can build is not very sophisticated and won’t carry big payloads. Put an outer concrete shell or some better passive defense, and maybe that will be enough.

As a result of some of my work only slightly related to telecom/internet infrastructure, I happened to get on the marketing lists for about six different Chinese companies that will gladly sell you a full size Shahed-136 clone complete with 2 stroke petrol motor. I wouldn't say that small paramilitaries being only able to fly a 5-10kg max size quadcopter with a munition on it into a datacenter is the limit of possible future capabilities. These things are cheaply made in fiberglass molds and look to be dead simple. They're already showing demo videos of them flying around with very low cost ardupilot capable flight controllers.

They even advertise the airframe and motor packages on Instagram....