The updated kernel is retrieved manually from mbp-ubuntu-kernel's github
releases, which is a temporary solution and should be changed back once
it's on the apt repo.
I've tested building this, and it boots and installs correctly, but when
booting into the installation it gets stuck after complaining about no
firmware for brcmfmac, and there's a red/green line on my display. This
is on a MacBookPro16,1.