To meet by chance means it happens totally by accident. To meet by design means the meeting is planned out.
I believe Ulrich set out with a plan to meet the Georg. Surely the Ulrich heard signs of the other in the woods. Georg was hunting in the woods that belong to Ulrich. Ulrich set out by design to find Georg and kill him:
On this fateful evening, Ulrich gathers a group of foresters to patrol the land in search of Georg. Separated from his men, he hopes to meet Georg alone and, when he steps around a tree trunk, he gets his wish. The two men face each other with rifles in hand, but neither can bring himself to shoot the other.
Ulrich admits that he was ultimately in search of Georg. Most likely, he knew Georg was in the woods hunting. It was a planned meeting. It was a designed meeting. Ulrich knew Georg was hunting. He gathered his men to search for Georg:
Ulrich von Gradwitz is a wealthy landowner. He has legal right to a disputed stretch of land but knows that Georg continues to hunt on this land. On the night the story takes place, he has organized a group of men to find Georg, whom he plans to kill. He considers Georg his enemy and calls him a ‘‘forest-thief, game-snatcher.’’
No doubt, Ulrich has designed the meeting. It is not by chance that Ulrich finds Georg. Ulrich set out to find Georg. It was definitely by design that the two of them should meet in the woods.