That depends on where you live and what you can afford for heating. Lol
Or your willingness to house your fish inside over the winter. At that point you can put anything in a pond. It’s just a really big aquarium you view from the top. Or even from the side if you raise it up and put in a window.
I have kept Uruguayan cichlids in outdoor ponds in Wisconsin May thru Oct, they did well, even with large temp fluctuations and readily spawned. The northern Mexican species did almost as well, although in a much narrower time window (June thru mid Sept)
Other cichlids from more tropical climates often died during cool spells.
The biggest problem I found, is visibility.
Most natural color species disappear quite easily under any natural conditions, so to see natural colored fish it is often best to have a very unnatural pond floor, if you actually want to see them.
Below is Australoheros sp Red Ceibal, in breeding color preparing to spawn in a shallow section (@6" deep)
Most of the time, they were invisible).
below Gymnogeophagus, seen when the sun hit perfectly
I overwintered all fish and plants Nov thru April because in Wisconsin, even 4 ft depth pond froze almost solidly through
Below Tilapia in a kiddy pool
Predators were also a problem, when ponds were sloped, raccoons had easy fishing, and I would find headless cichlid carcasses on the patio in the morning. So ponds needed to be dug at least 4 ft deep without slope to prevent predation.