I experimented a little using a Raspberry Pi 4 as a desktop Linux machine (a future blogpost), but it was not to be: it was far too slow to be usable, even if I did manage to make it work correctly with two 4K monitors.
So I returned to the idea of using an old Mac Mini for the job.
I installed Debian 11 Bullseye using the process I documented before. And, again, it worked fine.
But last time I did not care if the Wi-Fi module worked correctly or not. This time I did.
And it did not work out of the box.
This was not a surprise, but I did want it to work. Fortunately, it is just a couple of commands:
Install the firmware:
apt install broadcom-sta-dkms -y
And, after that, a reboot.
But, there we go: Wi-Fi support in Debian 11 Bullseye in a Mac Mini 2012, with hardly any effort at all.
(Note: I do not know if the Mac Mini will work under Debian 11 Bullseye with two 4K monitors. I await the correct cables to let me test this.)
Update: yes, it works with two 40k monitors. I need to have a tinker with screen resolution, but it works.