How does that integrate with the prevalence of stop-start engine technology nowadays?

In the UK it is only permissible if the engine is off AND the car is parked in a recognised or safe parking area. Engine off waiting at junction is not sufficient.

Stop-start is not sufficient to satisfy the criteria. This is now mentioned explicitly in the law.

It is the same in Germany.

Using your phone at an intersection is completely legal in Germany as long as you turn your car off. Not that anyone would advise you to do so.

May I ask for a source? I heard the opposite. Your car must not participate in traffic when you use the phone. It's fine if you're parked somewhere and have the engine off. But being parked at an intersection where people would expect you to react to traffic doesn't allow you to use the phone.

You don't have to interact with the ad. It goes away when you are driving again.

But if you did interact with the ad to accept whatever it is pushing, presumably you would be breaking the law.

It is not clear to me whether these ads are being presented in Germany, the UK or anywhere else where responding would be a violation.