Whenever I plug headphones into the Librem 14 laptop 3.5mm jack running Qubes OS v.4.2.1 the laptop spontaneously hard reboots. I am running the Embedded Controller v1.13 and latest Pureboot. Position of cam/mic hardware switch makes no difference.
Is anyone else experiencing this problem?
I have the same problem. Some weeks ago I got a reply from support that this is a known issue with EC 1.13. As a workaround one can downgrade to EC 1.12, but I care more about fast brightness adjustment than about wired headphones 
Thanks for confirming. I’ll keep an eye out for the next EC firmware release. Until then will make sure my headphones are plugged in at boot or use my USB headphone adapter.
Ah, cool, I did not know that plugging them in before booting already is fine. So thanks to you too!
I’m not sure what exactly resolved the issue but I’ve noticed that the spontaneous restart of the computer no longer occurs when I plug in the 3.5mm headphone jack.
Qubes OS did receive a minor version release to 4.2.2, so that may have resolved your issue.
I did some more testing after running into the problem again. I think I may have discovered the exact condition it occurs under as well as the workaround. I realize that my initial post said the switch position did not matter, so maybe there have been some updates that have partially fixed the issue.
If the webcam/mic hardware switch is off, then inserting the headphone plug kills the system.
If the webcam/mic hardware is on, then inserting the headphone plug works as expected.
If someone else running Qubes can test these conditions and confirm on another system it would be appreciated.
Your issues are not reproducible on my end, but the audio equipment I have is not typical, so that may be affecting testing.