Why?
In this case, the data will live for a few weeks at most. The goal would be a QR code that contains the data as a hash: https://forms.berlin/#[form data]. This is to avoid storing or seeing any user data.
I was also considering a P2P solution with WebRTC. This would let you transmit your form without the server seeing the data. You'd just need to both visit a URL at the same time.
The idea is that I can't store private information, and the Bürgeramt can't install any new software.