Never heard anyone say " How is you" but it make sense why they do that as I often wonder if there should be an ARE or IS. I have always associate "ARE" for plurals. Like "They are running" They = more than one person. But then again "you" is both plural and singular.
I grew up in a household of people from West Virginia so I'm am familiar to Appalachian mountain accents: The Dialect of the Appalachian People
Do You Speak American . Sea to Shining Sea . American Varieties . Smokies | PBS
