I like to have my MacBook Pro mid 2014 upgraded to Big Sur which is at the moment on catalina. It is because I want to have the newest System with security updates. I wish to have the installation with no risk. If I disconnect the IO Board before the installation, I think, then installing Big Sur is without a risk. The Board can’t be destroyed by a firmware update. Has someone done this already?
Workaround: I have the same issue with my MacBook Pro 15 Mid 2014. The only way to use the MacBook without the shutdown problem is using an external display or a HDMI dummy plug like this: https://www.amazon.de/gp/product/B072PV6... It is a hardware defect on the logic board, probably the i7 Processor with intel Iris Graphics. Maybe its the smc circuit. On Windows, I thought, I had no problems. But I saw some times the display goes black for 1/10 of a second. So I believe, it is the defect of the Onboard Graphic. My Problem occurred, when I used dolphin Nintendo WII emulator, which leads to 100% CPU usage und the fan full power. I think, the MacBook went too hot and this caused the damage.