In the desktop version of DC there is an option to scan qr codes from an image without needing to use the webcam. I think that this option should be available for all versions of DC.
(that desktop has such clears a long time mystery about the use of QR, as my person wouldn’t/didn’t know how to “scan”, having just one device.)
Having looked into the code a bit, not at all familiar with Android app programming and how it is organized, it looks like the QR code stuff is contained in an integrated third-party package “com.thoughtcrime.securesms” (stemming originally from Signal messenger if I understand correctly). Does that include the whole interface functionality for the QR reading in DeltaChat? I am just trying to find out where to change something if possible, to add phone screen or image file as QR source. Maybe in this case, a change would be needed to be made in the “securesms” package used by DeltaChat Android, and not in DeltaChat’s own Android code directly?