I use netcup, a german registrar.
They have an API access to change the DNS entries. I use a selfhosted tool called ddns-updater to update my DNS entries, so I effectively have it set up as DDNS

A truly open alternative would be Heliboard:
https://github.com/Helium314/HeliBoard

EDIT: one possible issue with HeliBoard is that swype input relies on an external closed-source library that needs to be downloaded and installed manually.

Ah, in that case I only know a handful of people personally that use Apple pay, but I do see some people occasionally pay by tapping their phone at the checkout

In germany, most banks that offer free banking (ING, Comdirect, DKB etc.) have switched from girocard to VISA/MC Debit cards. If you want an actual girocard, you’ll need to pay a monthly fee, either “directly” for the card (In the case of ING, Comdirect etc.), or by having a paid account in the first place (like Sparkasse, Raiffeisenbank, Commerzbank etc.)