I have a few questions.

In that system does the age verification result come with some sort of ID linked to my government issued ID card? Say, if I delete my account on a platform after verifying and then create a new one, will the platform get the same ID in the second verification, allowing it to connect the two and track me? Or is this ID global, potentially allowing to track me through all platforms I verified my age on?

What a verification process looks like from the user perspective? Do I have to, as it happens now, pull out my phone, use it as a card reader (because I don't have a dedicated NFC device on my computer), enter the pin, and then I'll be verified on my computer so I can start browsing social media feed? Or, perhaps, you guys have come up with a simpler mechanism?

In the Swiss system, it depends on what they verified. If they required your full ID, that has a document number like a passport and they could track that.

If they did the right thing and only asked for the over 18 bit, then they wouldn't have a trackable identifier.