That explains it then.
Thanks again for all your help.

Hi!

I have the same problem with a T460. It started off as an increasingly long time between pressing the power button and the manufacturer logo popping up, and now the laptop is refusing to boot altogether. I believe this might be due to a broken UEFI, so I wanted to try flashing the image that @plutomaniac posted on MEGA. ("Here is a temporary link with the full 16MB SPI image for the original T460 with its CSME firmware repaired/cleaned."). But the link was temporary and unavailable now! If you still have the file around plutomaniac, would it be possible to post it again? I would be super grateful.

I managed (half a year later :) to fix the laptop, but I did it differently. Instead of trying to find a working image somewhere and cleaning it using the guide, I dumped the SPI flash from the bricked laptop via an external flasher. Next, I ran corna's me_cleaner utility on the image. Then I wrote the cleaned flash onto the board and miraculously, the laptop works now. So for posterity, if someone runs into the same issue, try me_cleaner!