EU's specs for the digital wallet are available at https://github.com/eu-digital-identity-wallet, in case you didn't know.
I got an answer from the danish ministry for digitalization to a mail I sent them back in july, asking wether they were going to open source the danish version, and wether they were aware of the dutch Yivi app, which is OSS and available on f-droid, saying basically, yes they are aware, and specifically pointed me to the "Architecture and Reference framework" section of said specs.
Reading through all the documents referenced is a bit much for me, but I do find the basic principle sympathetic - User in control of data, no logging, nothing more than the nessecary shared in usage.
