We already have digital IDs in Australia, and it seems like a natural fit for this. The digital ID doesn't need to share much information with social media companies, it just needs to confirm your age. And then we don't need new 3rd-parties holding our personal information.

Also yes, voting is mandatory in Australia. You get a small fine if you don't vote.

It's a very good system. $20 is the right number to get you off the couch, but not so much as to cripple you. There are exceptions if you have a valid reason for not voting. The maximum fine is ~$180 so you can't simply ignore the Elections Commission and hope it goes away.