I have a Macbook Pro Mid-year 2014 that had the same issue.
I contacted local Genius for repair, they could not get anything but a blank black screen and advised I needed a new logic board at $500 my cost. I took it back home.
I then contacted the BBB SanJose office and opened a complaint online. Apple corporate denied any liability stating out of warranty and considered matter closed.
I finally located great information on Apple’s community forum here:
https://discussions.apple.com/thread/252034110?page=1
I contacted Apple support by phone and spoke to Senior support and stated Apple engineering has confirmed the issue and to search for MacBook Pro, Big Sur installation, I/O board, and corruption. The rep had me go through the usual SMC and PRAM, took a video of Macbook unable to start and uploaded the file to Apple. The rep gave me her direct email and we will continue to resolve once they have reviewed all the information.