Like many posters here, my birds have large houses, even larger runs, and are fortunate enough to graze acres of diverse and tasty greenery, together with its associated bugs. By the usual measures, they are happy (and tasty).
That said, there are times when I have to restrict them to their run, or the pasture is less diverse/in season than I'd like or the weather is forcing them into their house for an extended period. So, I'm working on enrichment which is reasonably weather resistent that they can duck under, climb on, run thru or otherwise play upon, and I took inspiration from
@Phaedra Geiermann 's Chicken Tower to build my own 3' dia, 3' tall layered dirt and greenery grazing tower, planted with things they might eat which will benefit their diet. Its located near the sometime-pond area where water collects when it rains (part of run management, moving rainfall away from the coops), so the area is nitrogen rich as it washes away the droppings. It also saves me work, periodicaly digging it out, in that I don't have to move the dirt far - just pile it into the tower and add fresh seeds to sprout...
Longer term, I'm going to need to expand the hen houses again, and probably start storing feed (and hay for the goats) outside the barn.