My prediction is that it will soon be a requirement for all websites and apps with user-generated content to require authentication with the UK government's Digital ID OAuth provider and that requirement will include linking the user's username to their Digital ID. It won't require websites and apps to pay a third-party provider to check users' identity, so the UK government can argue that it doesn't place a disproportionately burdensome cost on smaller websites and apps.

After the UK implements this, other western countries will follow. For example, here in Australia, it's a simple solution to the under-16 social media ban which is about to come into effect. The bill was given deliberately weak verification requirements so it didn't seem too big-brother, but I'd bet real money that there's already an amendment in the works to tie it to digital ID after they discover what everyone already knows (i.e. that it'll be easily bypassed), followed by another amendment to tie the digital ID to site/app ID, for online safety reasons of course.

In time, websites/apps may offer your government's digital ID as an alternative to their in-house identity provider. If this becomes globally ubiquitous, many of them will stop maintaining their own authentication and rely solely on government ID providers. The identity provider you use will depend on where you are, so VPNs will become useless.

This was all inevitable from the day the internet opened up to everyone. Governments have an insatiable desire for power and limitless paranoia about threats to their power.

Internet peaked too early to build any countermeasures for this.

I remember when the Internet was celebrated as decentralized media, allowing common citizens to criticize repressive regimes. Today it seems like the west is emulating the countermeasures already perfected by those repressive regimes.