Google Play to revoke fullscreen notifications permission from newly installed apps that don't provide calling or alarm functionality

Probably all apps that has some voip calling functionality.

Whatsapp, messenger, viber (is that still a thing?) and similar

Edit, just saw

Unless they provide call or alarm functionality

So they should be safe

Possibly some security related apps to auth for banking and stuff, not sure how they work behind the scenes.

Same goes for some 2FA apps i guess?

I don't install anything that has ads so I can't confirm this, but I guess apps that show fullscreen ads?

They are used to push through the lockscreen e.g. when you get a call or when a timer finishes. I assume camera apps might also use it for the button shortcut (double-tapping the power button opens your camera in most Android phones). If the app doesn't do calls or alarms of some type, I can't really think of any valid reason why they would need that permission unless it's something weird like Tasker and you want it to.
Other permissions that are also "revoked by default" like this are using the accessibility services or drawing over the screen - you just need to have a popup in your app that says "the app needs \ to work, please enable it in the following screen" and then opens the settings page.

You have to opt-in to those already. This isn't blocking applications from being able to do full screen notifications, it's just defaulting it to disabled so you have to opt in.