There are at least two options to verify age without humiliating procedure of taking a selfie with a passport like a porn actor.

First, there are USB tokens that can hold a private key and sign messages. Such tokens could be sold at places accessible only to adults and verify that they are indeed adult. Obviously every token should hold the same private key.

Second, OS could implement "parent mode" which allows installing only white-listed, government approved apps (no Telegram or Whatsapp or other dangerous apps, but school apps are ok) and opening only white-listed government-approved websites. Put in jail the parents who did not set up a parent mode. Problem solved without passports and verifications.

If, however, the government insists on selfies, it means they just want to identify users and compile lists of "untrustworthy", "rebelious" and other persons of interest.

Also, employees who do verification, sometimes create internal chats where they post pictures of clients and mock their appearance. We had such case with Alfa-Bank in Russia, where the photo of a funny client with a passport and third-grader level comments leaked to Instagram account of employee's friend. The bank paid approximately $20 as a compensation.