A few moments ago I wanted to shut down my laptop and got the standard question whether I would like to install updates in the process. I checked the box and was very surprised to see my ThinkPad reboot into a black screen only saying "Please wait while we install a system update" and a rotating /.
After a while, my laptop shutdown and I could reboot normally. But what happened and what was this message about?
EDIT:
Before running into this issue, I loaded a firmware update via Gnome Software and have not previously shutdown the computer. Was the "weird" update process result of this firmware update?
You're describing a Thinkpad firmware update. To confirm this, run
fwupdmgr get-history, check the firmware date, and search for the checksum (SHA1 hash) via your favorite search engine. You should see your update package within the Linux Vendor Firmware Service list. The blog post you found was on the right track.