What's the actual situation in practice for the granting of a PPKK?

There's this thing called a PPKK which is supposedly from what I can tell available to anyone who has an ethnically Czech ancestry from Czechia.

On the surface it looks like technically anyone who can trace their ancestry to one ancestor, even a very distant ancestor. Like as distant as a 5th great grandparent with a Czech surname like Novotny or Dvorak who lived in the country can get it and can easily get permanent residency in Czechia.

But what's the actual situation in practice for who qualifies and what do you need to do and what's the furthest back ancestor that actually qualifies?