I’ve used the vmdk file out of the first post and did upgrade it with 4.12.
A few things I did afterwards:
* updated to 5.10.0-22 kernel and modules (debian bullseye)
* added all customizations from sinn3r back in
* added a few modules and libs (sorry, image became a bit larger)
* dr_bcu2 error on initial boot, but after uploading the correct KNX device, this is resolved

So you need to to save your retentive memory first, deploy this image, upload project and restore retentive memory.
Now trying to find a site where I can share 600MB easily….