You can sign up for email notifications after creating an account on ipsw.me. Been using this service for many years now, works fine. Emails arrive only minutes after new releases.

I have no idea. I usually just wait until there’s the red circle thing on the settings app lol

I'm in a discord server that pings every time there is a update

Macrumors.com

There is an option for automatic critical updates

Someone on this sub will always post it within the hour normally

Visit the r/apple, r/ios, and r/iPhone subs every day. At least a dozen people per sub will post the second it is released.

I usually check daily around 1pm my time but especially on Tuesdays. But given that my News widgets are for “Apple” and “Technology” and that I follow every Apple product sub for a product I own, I’m usually made away fairly fast