What do you consider rural?
No medium or large cities or suburbs by most conventional definitions. No city or town over 50,000 (that may even be large; I'm from Detroit suburbs where at least a dozen suburbs are that large). Universities are OK to have in rural counties. What the census bureau would consider 60% or more rural.
It appears there were just a few holdouts in 2016, and even those are iffy.
Oktibbeha, MS is probably your best bet, but its no where near as White as the counties mentioned in the OP
And, Griffin's map still has its whites voting 70-27 Trump. I guess there are a few liberal professors who snuck in there or something!