Ultimately, it proved insufficient in pegging back the Seagulls, following a first-half double by Pascal Gross.
A scramble in the box saw the ball hit Diogo Dalot and roll goalwards, only for Brighton keeper Robert Sanchez to divert the ball into his own net via Alexis Mac Allister.
It is the first time United have kicked off the season with an own goal since 2015/16.
Back then, it was Kyle Walker who turned it into his own goal in what would be the only goal of the game at home to Tottenham Hotspur, when he beat Wayne Rooney to the ball but deflected it into an unguarded net.