Note that this is a rather critical regression (since it used to work
fine with previous bullseye ISOs), that is currently preventing
installation of Debian on the Raspberry Pi 4, i.e. by far the most
widespread ARM64 platform out there.
Quite a few people are negatively affected by this bug, and one can
expect a lot more to be if Debian 11 goes to release without the
inclusion of mdio-bcm-unimac.ko in the netinst ARM64 ISOs.
I have created an initramfs-tools merge request to attempt to fix the
problem, which can be found at:
https://salsa.debian.org/kernel-team/initramfs-tools/-/merge_requests/46
However, since I am not entirely familiar with how netinst ISO kernel
modules are generated and picked, I can't vouch that the proposed fix,
which consists of referencing the mdio/ subdirectory for inclusion, is
the proper way to go...
