We been successfully repaired many home button with Touch ID for older models. But none of those are cracked on surface. Most of them are ribbon flex broken, or either water damaged which still able to repaired.
If your case is like photo at below...
|iPhone 8 Home button cracked|
|As long it's original button and surface OK, we can repair it.|
- Touch ID surface cracked - Can't repair, sorry
- Touch ID flex broken - Can repair as long as you have the original button
- Home button not working and Touch ID works - Can repair
- Home button works and Touch ID not - Can repair if it's original button.