It does. But official images are made using --target virtualbox as well as --target qcow2. I don’t do separate builds. That’s why virtualbox guest additions and kvm qxl stuff is installed in the same images. Until this day this non-ideal combination was doable, now something breaking was introduced. I don’t do separate builds of virtualbox and qcow2, because that would make the already very time consuming build process (a lot is already taken by the qcow2 xz creation) even more time consuming. Each time I am regretting not having left creating builds to the kvm maintainer, i.e. you.
make 50-qxl.conf somehow not interfere with VirtualBox
I have no idea how to do that.