Smoke, probably just had an engine change & it looks like the first start burning off inhibiting fluid.
Spot on after an engine change, and as another writer mentions I would have advised the tower that a smokey engine would be starting, and not to sent the fire trucks.
This is not a normal engine start prior to aircraft pushback.
Note the heavy wheel chocks still in place, the undercarriage doors are still open, flaps partially lowered and maintenance steps still close to the fuselage.. post engine change first run-up.