iPhone 12 back glass repair

Certainly. I'm going on the following three bits of information:

1. The back glass repair option for AppleCare+ only applies to iPhone 12 and iPhone 13 models, and again assumes there is no other damage (such as damage to the metal frame band). -- credit: Michael Black ASC
2. Apple will stop replacing the whole iPhone just to repair Face ID sensors or cracked glass - iDB
3. AppleCare Products - Apple. The following image is taken from this article:

Lawrence, I found this in the knowledge base article:

"What if I have AppleCare+ for iPhone?

AppleCare+ gives you expert technical support and hardware coverage from Apple, including accidental damage protection. Each incident of accidental damage is subject to a service fee. 

If you don't have AppleCare+, you'll pay the out-of-warranty fee for that type of repair.

 Screen-only or back-glass only* damageAny other damageAppleCare+ service fee$ 29$ 99

* Back-glass only repairs are available for iPhone 12 and iPhone 13 models only. Terms and conditions apply.

Not sure if you're covered? Check if you have AppleCare+ coverage by entering your iPhone serial number. 

Learn more about AppleCare+

See out-of-warranty fees for iPhone screen repair"

According to MacRumours this went into effect on September 21, 2021. But I cannot find anything in the article regarding repairing the back glass WITHOUT AppleCare +.

Yes. Apple now does back glass repairs for iPhone 12 & 13 models. The cost involved should be covered in the following article:

• iPhone Repair - Official Apple Support

I hadn’t seen anything about that, and it isn’t mentioned in the link you posted. Do you have more information?

Just so you know, IF you purchased AppleCare + the cost is $29 unless you have other damage and then it is $99. There is no such price available if you do not have AppleCare + and apparently you have no other option than an out-of-warranty replacement.