I would dig a hole to below your frost line. Pour a pier in the hole 7-8” or mor thick. Make sure the concrete is cone shaped with the top being smaller than the bottom or a perfect cylinder so the frost can’t grab it. Let it cure for a day, then coat a 6x6 ground contact post with tar or equal to just above grade and backfill. After the backfill settles add some dirt around a bit higher than the finish grade. Overkill, yes indeed! Doesn’t cost hardly any more than any other way, but will last thru your grandchildren's lifetime.
They will say my grandpa always did things right and you may roll over in your grave with pride
