[shmel]

Gradually. It will be used to provide your freedom back. Lockdown is still in place, but if you agree to use the app, you can go outside and chill in a park, maybe even meet up with family members (groups fewer than N). Then you can introduce checkpoints in public places (just like China did btw): wanna go to malls, cinemas or airports? Install the app. But no, you are not forced to do this. You can just sit at home if you'd like until the lockdown is fully lifted. But we can't tell you when it happens, nobody knows. Perhaps after everybody is vaccinated.

Surely, they can also add a smartphone-free version that is a huge pain in the ass to use. It checks the box "you can survive without smartphone", but makes it practically unreasonable.

It will be the same situation as with CCTV and bag searches nowadays. The vast majority of people will accept this as reality and perhaps even support this. London is full of CCTV and mostly people are okay with this because they believe it is for their own safety. Sure, you are not forced into this, feel free to live in mountains off-grid.

The bottom line is you just wait until the lockdown is normalized in people's minds and then reward them with freedoms if they agree to use the app. And 99% will be okay with this.