I've confirmed that this fixes network interface detection in a Xen installation with apt-setup/proposed=true, and that xenbus_probe_frontend is added to /etc/initramfs-tools/modules to ensure that things work properly after installation as well.
Separately, I've confirmed that a non-Xen (in fact KVM) installation still works as normal, and doesn't have xenbus_probe_frontend loaded.
I've confirmed that this fixes network interface detection in a Xen installation with apt-setup/ proposed= true, and that xenbus_ probe_frontend is added to /etc/initramfs- tools/modules to ensure that things work properly after installation as well.
Separately, I've confirmed that a non-Xen (in fact KVM) installation still works as normal, and doesn't have xenbus_ probe_frontend loaded.
Marking verification-done.