The one point that's still a bit intriguing to me is the nature of the burn. I'd love to see the report on the origins / spread of that fire.
The internal cabin photos reveal a mechanical wreck but not significantly bad fire damage. The roof OTOH.....
Was it really oxygen bottles? Or is the roof area naturally more combustible?
Assuming a fuel leak fire that wouldn't be the shape of the fire damage I'd expect. Then again, I'm no expert.
This is of course secondary to the cause of the accident but fits in with stuff like cabin safety, breakup locations etc. (all not easily managed due to variables)
From my view the RH engine probably caught fire from scrapping all it exterior component (fuel-oil sources) in an environment of sparks including any breaks in the engine casing. Unfortunately this fire which was visible early on was nestled against the RH fuselage where there appears to be a buckle fracture in the tube. This could now expose the interior to an ignition source. No need then to wait for the aluminum skin to be burnt through in a pool fire.
Once the interior starts to burn it looks for sources of air above the flame and makes it way to the ceiling panels inside the cabin. Smoke is your problem here, but even now it can remain localized until somebody opens a door. Then it rapidly migrates towards fresh air. That's probably the most significant part of this as to when and how the flame front spread.
Will see what the NTSB fire experts say in their final report about the timing of the fire spread vs egress of the passengers