Also, the area where the original ACARS messages covers is just forward of the galley service cart bin. A timed device on a service cart (the one that brought the Metrojet down was the size of a 12 oz drink can) soule easily have started the cascade of events.
Another thought, the forward EE bay is not locked, and has a service access door that any ground handler can get to. That electronics bay is big enough to get into and walk around in, it is not some small compartment. It has racks of equipment in it and I doubt you could find any maintenance tech that could tell what should be and should not be there. I have been in them and it looks like some science fiction space ship control. With just a little work, a device could be planted in there that looks like it belongs.
Will we ever get the truth? Egypt controls the investigation, and any cause other than mechanical failure will negatively impact their tourist industry.
Actually, the area where the first messages affect aren’t near the service cart bin. They’re inside the cockpit ‘wall’ and there’s significant separation. There would also have been galley smoke messages and perhaps cabin smoke messages.
Like I said, the ACARS messages don’t eliminate terrorism, just the common methods. An incendiary (not a bomb) planted in the avionics bay would account for it - but so would defective avionics batteries.