Travelling salesman is about finding the shortest/cheapest path that visits all nodes. I don't see why you'd want to involve all nodes for a payment route. If

Travelling salesman is about finding the shortest/cheapest path that visits all nodes. I don't see why you'd want to involve all nodes for a payment route. If you meant "shortest path problem" instead, then it seems that route planners for road networks have already solved it reasonably well. I suspect the challenges for lightning have more to do with keeping the map up to date.