I had my Ridgeback in a small unit (no yard) successfully.
I'd take her out for long walks twice a day, and when I could, arrange for a neighbour (who all loved her), to look after her during the day so she didn't get bored out of her tree.
If the weather was suckful, I trained her to walk on a treadmil (only ever slow walk speed and under constant supervision) and she loved it!
And, when I could, I'd take her with me wherever I was going.