Germany's app (AusweisApp2) is open source and available for literally every platform. Linux, FreeBSD and even Fdroid included.

I'm not sure of the exact functionality and whether the government can track anything. You need to scan your ID, the app will then ask for a PIN (2fa) and then will tell you which data will be sent to whoever made the request.

Authentication is done through an eID server which in theory anyone can set up. The requirement are quite strict though so right now there are only three providers. They check the validity of the ID and request and send the received ID data to the requestor.

It's quite the complicated procedure to ensure the highest possible security and privacy.

The entire process is publicly documented and you can probably spend a few hours trying to understand it.

As for locking people out of online communities: I don't think it's a problem if and only if the legislation applies exclusively to social media providers above a certain size. Such as having 5 million+ monthly users.