Hi David and welcome to the forum:
I have had the Canon EOS 60D (3 of them) from about 2011 until recently, so I hope I can help you.
Normally you will get an error message that a firmware update has turned to custard, so there is a good chance that it is not corrupted. Considering that you are getting a display in movie mode suggests to me that the camera can turn on ok, as to do so it does a self-check.
So, let's try some diagnostic procedures:
What happens when you press the Menu button. Do you get to see a display on the LCD panel?
Have you tried, using the camera in M, Av or Tv modes to see if you get the display and also tried pressing the INFO button to cycle through the displays to check that your LCD is not set to blank display?
Try to reset the camera to factory default. Check your manual if you don't know how. Always do that first when your camera doesn't do what you think it should or how you think you set it to work. If resetting doesn't remedy it, I fear all is lost if a corrupted FW install went south as Canon does not service that model. Perhaps a private camera repair shop can but not many will be able to, if any.
It's very difficult to debug those failures as the system is not yet up and running properly. Sometimes nothing interesting happens and the FW fails. That's why a private shop may not be able to restore it if you experienced a FW fail. Try the reset first.
For future reference never upgrade FW before reading what the FW upgrades or "fixes". It may be something that doesn't affect you so the upgrade isn't necessary. At any rate Canon FW upgrades are cumulative so you don't have to do each one if they don't affect you and a later one does.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.