Fixing headphone audio on Libreboot T480s

[absent]

Lenovo ThinkPad T480

Lenovo ThinkPad T480 (+libreboot) NOTE: All of this has been tested on a Vanilla QubesOS 4.2.3 (XFCE + latest updates) install with LibreBoot 20241209 being the firmware. I tested most of this functionality on another distro before to rule out hardware damages or QubesOS-specific stuff. So when I’m saying “XYZ is not working” I do not mean “it’s not working on qubes/dom0/xen/…” but “It’s not working on ‘regular’ GNU/Linux, but it’s ALSO not working on QubesOS 4.2.3” When I say that “libreboot …

I also found a trick a while ago: it takes only few clicks. Please see the heads report for t480. It should work for libreboot machines too