AFAIK there is nothing in Sartarite law or custom to prevent a
non-Barntar devotee to manage a stead. As long as you are an active
member of your clan and you attend the necessary worship ceremonies to
Orlanth, Ernalda, Barntar, Heler, Uralda, Esrola, and whichever deity I
forgot right now, it doesn't matter much which of the clan's deities you
value most. This includes Hedkoranth the Adventurer (formerly known as
Orlanth Adventurous), Issaries (Harst or even Garzeen), Lhankor Mhy,
Elmal, Humakt and Urox. Heck, if Argan Argar is an acceptable deity, why
shouldn't Urox be?
Of course you can't go the whole way to a deity of destruction if you
want to retain some of the fertility functions you need as a
steadholder, but Orlanthi myth shows clearly (in Orlanth woos Ernalda)
how destructive forces are involved in fertility. In Exile Tarsh, even
worship of Maran Gor doesn't seem to prevent you from gaining some
nourishment out of land or herds.