https://www.newsweek.com/us-russia-emergency-alert-drills-1831776
I think it's unlikely they're going to be broadcasting a 5G kill wave signal, or installing anything on your phone.
Announcing a declaration of full-scale war on the other hand? That actually seems more likely.
Seems perfect for some fuckery to be done and have the panic-mongering, aswell as the plausible deniability from the announced test to make everything exponentially worse.
I personally believe that nothing relevant for the big picture will happen, but let's keep an eye out, just in case.