One of the videos I saw had sound.
There was a fire and it sounded like small arms rounds cooking off.
“There was a fire and it sounded like small arms rounds cooking off.”
Those were fireworks, stored in the same or adjacent warehouse. These might have ignited the large explosion.
I concur.
fireworks factory next door
You are correct.
From the footage, in my limited Army/Marine e-BDA opinion, the flashes and their sounds were from warhead detonator’s being set off.
As well, Lebanon has very limited “possible” related production at all -
https://trendeconomy.com/data/h2/Lebanon/3604
And those types of nitrates would not arrive and derive from specialized Russian tank-containers in 2013-2014.
Contrasted with China, which makes about 95% of the worlds fireworks.