Deathfuzz

If she did stay in-system, Ashyn would be my guess for where she set up. Cultivation would most likely want to stay in an inhabited planet to align with the shards intent and unlike Roshar and Braize, Ashyn seems to have been abandoned/ignored by Odium and Honor after humans and Odium traveled to Roshar. We also know from wobs and the state of the sanderson that we will be getting 1-2 books set there (Silince Divine + Unknown title) and the disease based magic would align more with cultivation than the other shards.

The shard plate pieces appearing is what gave him away. They seemed fine with him having a blade but no oaths when he was let in.

It might involve the group collectively believing that the individual is one of them, and that shared perception/connection is enough. If that's the case, then it would have to be genuine belief which would be very difficult to achieve depending on the culture.

Since the appearance of Returned is based on perception, I always assumed that the line of succession restriction only applies because they believe it works that way. If Shallan has similar abilities she might be able to unconsciously change her hair color because she both believes that its possible to change with lightweaving, and because she had a habit of lightweaving without realizing it previously.