What about a new mixed-feed which merges the Subscribed, Local and All feed based on probabilities customable by the user e.g. 10/40/50 or 0/20/80?

This would push users toward local posts (especially on smaller instances) while still supporting a better distribution of user engagement over the threadiverse. And if you don’t trust that it was implemented correctly – you can simply check it by counting the amounts of posts against your chosen probabilities.

Edit: changed feed name to mixed-feed