Firmware upgrade on ThinkPad

I do not know what could have been the last thing causing that much headache as the HDMI problem of my current laptop. After a succesful system update the external monitor was not recognized and stayed in a disconnected state. I spent some hours browsing false-positive forums hunting for a solution. Then I gave up and turned to the problem of updating the BIOS which in turn happened to be the solution to my display problem.
I was inspired by an article how easy it is to upgrade firmware on Linux nowdays. Of course my ThinkPad 13 is not supported by that... But at least it ignited my curiousity. Downloading the .iso image from the manufacturer's site was easy. To burn it on a pendrive - that was something! Lots of tool around the world to burn images, but noone tells you to unpack the .iso image first to a .img file. That was the missing link that I have learned from this video.
The main parts:
Thanks nixcraftcom!