Ask HN: What cities are tech friendly in Germany?

Berlin, hands down. That said many other places aren't particularly 'tech-unfriendly' either. It really depends on what you want to be working on and in which role (consultant, entrepreneur, employee etc.).

Berlin is startups all the way but finding consulting/ freelance gigs there can be more difficult than elsewhere and the rates tend to be lower.

Rhine-Ruhr mostly is SME, heavy industry and marketing / media (Cologne and Düsseldorf in particular). There are coworking spaces not unlike Betahaus there, too (Unperfekthaus, for example).

The dominant industry in Frankfurt is finance (and logistics to some extent due to Deutsche Bahn).

Similar aspects apply to the other metropolitan regions.

To bring some context I am a software engineer within the JVM space (Java, Scala) and additional work experience in front end like with libraries like angular and vue

Berlin. You can't go wrong moving to a city with a place called Betahaus (edit: in betahaus.de you can see they are also in Hamburg)