Once a day here.
Dogs require long breaks between meals so that their digestive tract can break down food more efficiently emptying out the digestive tract as much as possible before more food is consumed. This is their natural design. Humans, on the other hand, are hunter/gatherer types with a digestive system designed for "gathering" - much smaller meals more often.
So, adult dogs usually gets fed once or twice a day. Bullie and Gizmo can handle twice a day meals. Angus can't. His poop gets big and soft if he gets less than ~24 hours between meals. So, I'm on a once a day schedule with a handful of their kibbles for treat/reward throughout the day.