I notice that Microsoft’s Project Mu has a PrintScreenLogger tool (Ctrl+PrtScn):
and that it is already getting some forks:
Before that, there was RU.EFI command line tool (F12):
and Nikolaj’s CrScreenShotDXE (LeftCtrl+LeftAlt+F12):
And there are probably a few other options I’m not aware of, including by IBVs/ODMs.