A few options: (a) load a digital copy of an existing ID into your OS's wallet app then the wallet app can simply attest to any service that the device is owned by someone over 18 (b) sell single-use tokens in grocery stores that require an ID to purchase like alcohol. token can be used to verify you're 18+ for one site. (c) require that any network-enabled device can only be bought by showing ID to prove 18+ and then when set up can be configured at the OS-level as child-owned so a parent can buy a device and do the initial setup so it's locked in child mode.