The EU is already implementing this in the best way it's ever going to be implemented:
https://digital-strategy.ec.europa.eu/en/policies/eu-age-ver...
I really don't like this perfect law enforcement future, but this EU initiative is about the best design one can have.
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Almost. Their apps will only work on Apple and Google-controlled phones.
There are no plans to allow separate, standard AOSP attestation methods for Android. Google's crooked* Play Integrity will be the only one.
*crooked because it confirms Android 8 are safe and with full integrity, even when they're rooted, full of malware and present spoofed certificate.