Horrible smell in bath tub drain after water runs a few minutes, its not a sewer smell or moldy smell,had it snaked, called a plumber, tried everything I've read on line & still it smells, help, where do I go from here

I would suggest to remove drain plug use a hooked coat hanger to reach in and grab at anything caught up in the P TRAP of the tub drain, Next before you go to bed in the night mix ½ cup baking soda ½ cup table salt pore in the drain, add a cup of vinegar leave it overnight first thing in morning pore a bucket of very hot water in turn on the tub water to flush out everything out hopefully this will work for the (the smell is from the hair and soap), Thanks.
John