To add to BDL last comment:
The acidulated milk alternative to buttermilk works fine in baking where the tang (and possible reaction to baking powder) are the desired effects. With fried chicken, eh, not so much. Buttermilk (and I could go on a tangent about "grocery store buttermilk"--I used to sling pancakes after all, but I won't. Just yet) when working with meats is all about the culture. I suspect that your fried chicken will involve a buttermilk marinade. The beauty of this method is that the buttermilk does several fancy "cooky" type things all at once.
1) Marinade (duh). The culture in the buttermilk will affect the meat in the ways that oil/spice/acid marinades would. That is help 'soften" or tenderize the meat by breaking its protein structure down (yes, I know, not the best way to describe it but we prep'd a wedding tonight and exhaustion trumps accuracy). It will also flavour the meat as any marinade would--however that flavour is a neutral "tang." Which, when frying, is exactly what you what to play against the fat and crunch.
2) Degourge (or milk): Buttermilk is still milk and will degourge your meat, that is draw out "nasty juices" and "bleach" your protein. Just like we do with liver, as an example. It may not seem like a big deal but it really helps the look of the final product (brilliant white meat against the golden crust, no red bits that make you second guess your timing).
3) Binding. The viscosity of buttermilk ( I suspect) is what is going to hold your breading to the chicken. You use buttermilk, you don't need eggs. Milk and lemon juice won't help you at all in this department. And really, this is AMERICAN FRIED CHICKEN, right? Not Tempura. Save the eggs for the potato salad.
Right, got that off of my chest. As stated before, if you really can't get buttermilk use yoghurt, thought you might have to thin it out. And please use an active culture yoghurt.