(I'd say this is a hopeless case. This basically is a complex computer with additional complex electronic stuff. On bootup, plenty of checks are done in all parts of the receiver, if something fails, it shuts down. If the fault appeared in the HDMI section after some voltage spike - you are not going to fix that board, that one is "exchange only". *If* it's that board. After all a working second receiver to swap parts to narrow down the issue is IMHO the best way. Which makes it financially unattractive, but might be a fun educational project.)
That said, the HDMI flex cable might not be full seated, and that front PCB seems oddly warped...