I'm on Ubuntu 18.04 with my Lenovo Thinkpad T460s. After an update a couple of weeks ago I did a reboot and I saw something which included the word "EFI" in the top left corner of my screen. Then everything went black and unresponsive.The laptop started system beeps every 5 seconds or so. I had no idea what was going on and tried to push the power button numerous times. I typed on the keyboard. Nothing. I was convinced something was terribly wrong. Nothing worked and since the laptop has a built in battery I could not cut power (probably a good thing in this case). After a couple of minutes the beeping stopped The laptop booted as normal. I had no idea what happened and whatever it was I was not given much forewarning or information. No way to see what it says while that message flashes by up in the screen corner.
I do know that a package with the word "firmware" in it was updated that day, but not exactly which one. I did check my bios and it's very new, from July 2018. I have not had Windows on this machine since I got it 18 months ago. I still wonder what this actually was. Anyone?
Update: I just read this about LVFS: https://www.omgubuntu.co.uk/2018/08/lvfs-lenovo-firmware-updates-linux
Could that be what I experienced?