Forgot my screen time passcode and there is no option for changing it

These are the minimum requirements to reset the ScreenTime passcode:

• The device must run iOS/iPadOS 13.4 or later;
• You must know the Apple ID & Password that were used to set up that ScreenTime Passcode;
• If you are part (member) of Family Sharing, ask the Organizer.

If you meet ALL above requirements, these are the instructions:--> If you forgot your Screen Time passcode – Apple Support

Shouldn't be this case, you need to erase that device following these instructions (even if related to the passcode to lock/unlock device's screen):--> If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

The bad news is that you cannot restore data from a backup, since the ScreenTime passcode would come back in.

Regards

Giulio

To unlock your iPhone, follow the steps described in the Apple article:

(< iOS 15.2) -> If you forgot your iPhone passcode

If you forgot your iPhone passcode - Apple Support

(iOS 15.2 and newer) -> If you see an iPhone or iPad unavailable message or Security Lockout screen

If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support

See -> If you forgot your Screen Time passcode

If you forgot your Screen Time passcode - Apple Support