From anecdotes around me now I live in Berlin, I believe it extended at least into Brandenburg.

Even in 2019, some coworkers were complaining that the best offer from their landline company (in one of the small villages just outside the Berlin city limits) was dialup.

Berlin's reputation post reunification has been "poor but sexy".

Nah, I’m talking 2016. I have no idea about commercial internet outside Berlin. But my residential connection in suburbs of Aachen in 2015 was copper.