Voadam
Legend
It is a sprawling mess.The problem is that "priests of a specific mythoi" and "specialty priests" aren't exactly interchangeable; in fact, "specialty priest" doesn't even exist as a term in the PHB. In addition, each book that discusses priests, kits, and multiclassing combinations in general has it's own rules, making it kind of a mess to figure out what should or should not be allowed.

I think that you have to look more at the individual source and not mix and match applicability.
I am agreeing.I did acknowledge that COYOTE THIEF! was not something most tables would approve of, exactly due to things like this.

Sort of.When looking at Legends and Lore, do remember that this book isn't about demihuman deities; if the priesthood calls out that you can multiclass it states that this is an exception to the rules about humans not being allowed to multiclass.
Take Isis priests.
"Priests of Isis are, in actuality, multi-class wizard/priest characters. In the case of human worshipers, the normal prohibition against multi-class characters is waived."
This mentions that in the case of human worshipers it as an exception for humans, but this phrasing indicates humans are not the assumed only case.
Later in the Ravenloft book Domains of Dread it explicitly adopts a number of Legends & Lore pantheons as the default worshipped pantheons for different native Ravenloft demihumans.