You can hear what sounds a lot like the very distinct sound of the RAT having been deployed in one of the videos. There is also no main turbine sound. This really seems like dual engine failure, for whatever reason.
I saw you mentioning this but the RAT on the 787 sticks out of the bottom and should have been visible at around :04 seconds into that video when the aircraft silhouette is visible clearly against the background.
Although it's possible I am just missing from the video. You are right that the sound is quite distinct and can be clearly heard in the video.
The RAT is surprising tiny on the 787, and this is a phone video of a monitor, then run through Reddit compression. I am of course not 100% sure about any of this.
Yeah I saw that picture and came back here. I think you are 100% right that the RAT is deployed.
From the video of the runway it also seems like the aircraft didn't do a short takeoff (ADS-B location data is always crappy on the ground in my experience so this is entirely unsurprising).
There was a "smoke cloud" from behind the left engine which could also have just been a dust cloud right after rotation.
The flaps allegedly could be at only 5° (which is why they're so hard to spot) because of the runway inclination.
https://old.reddit.com/r/ahmedabad/comments/1l9i1ga/om_shant...
https://en.wikipedia.org/wiki/Ram_air_turbine