Hi Bob. I have once been to the farm Papkuilsfontein (outside Nieuwoudtville). We did a short day hike, but it was beautiful and its a really nice (family friendly) farm to stay at. There is a big canyon and waterfall which is either Oorlogskloof itself or similar to it. I see the Oorlogskloof nature reserve also has some day hikes, and a cursory google showed other options for short day hikes around Nieuwoudtville. Not sure if overnight hikes will be allowed yet. Perhaps a trip to Nieuwoudtville is on the cards?
Another obscure project (depending on your appetites) could be to climb the highest peak in the Northern Cape, Murch Point. Theres some information on this website, not sure how much of a hike it actually is https://www.ninepeaks.co.za/the-peaks In fact, I think the point is more accurately a trig beacon than an endearing summit. But it may be a fun project.
Hope the info is relevant