I got my iPhone screen repaired and it now says "iPhone Unavailable"

You can sometimes remedy this without a computer if on iOS 15.2 or later, but you will still need the Apple ID password. It will WIPE the phone.

How to reset your iPhone, iPad, or iPod touch when you forgot your passcode - Apple Support

The article is in error, the screen looks like this

Was the screen repaired at an Apple Store or Authorized Apple Service Center?

• Yes (very unlikely). Return there and seek assistance.
• No (highly likely). You had an unauthorized repair performed on your iPhone. Apple can no longer assist you with this iPhone.