Make it user specific. Feeds are combined solely from the individual user’s perspective. Consumption would be easier but submissions are still federated.

Advice on choosing between two things that are only marginally different.

Or just make it user-side. Let users create their own feed combinations. They’d still have to select a specific instance for posts.

Feeds would be consolidated but posts and comments will still be federated. And one user will be unaffected by how another user organizes their feed.