I think it is replaced by Permission Manager on Android 10. You can find it from Settings → Privacy→ Permission Manager, where you can manage apps permission.
No, permission manager has been and is still there but app permission monitor can show you live "monitor" or history. so you can get notified when you want app "x" to notify you if it sends sms, location, camera, storage etc. as you can see in screenshot, there's the button in the middle for "permission history" and each app you can configure what you want to get notified of app use a permission even though it's already permitted. I think the closest one to android 10 is "notification monitor" but that doesn't allow you to configure what permission you get alerted
