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.
India is getting the signal today, too: https://m.timesofindia.com/world/us/this-is-a-test-all-need-to-know-about-us-govts-nationwide-emergency-alert/articleshow/104148465.cms
This article says nothing about India getting an emergency test. It's an Indian news article telling details about USA getting emergency test.