Chop half the plums. Put halved and chopped plums, the chile, and green onions in a deep medium bowl; set aside. Microwave vinegar and 2 tbsp. sugar until steaming, about 30 seconds, then stir until sugar dissolves. Put ginger, mustard seeds, cumin seeds, bay leaf, crushed coriander, and 1 tsp. each salt and pepper in a small bowl.
Heat 2 tbsp. oil in a small frying pan over medium-high heat until shimmering. Add ginger mixture and cook, stirring, until mustard seeds start to pop, 15 to 30 seconds. Remove from heat and stir until cumin seeds are a shade darker, 1 to 2 minutes. Add vinegar-sugar mixture. Stir into plum mixture and let chutney stand at least 1 hour and up to 3 hours, stirring occasionally.
Meanwhile, heat a grill to medium (350° to 450°). Combine remaining 1 tsp. each salt and pepper, the ground coriander, and lemon zest in a bowl. About 20 minutes before serving, rub pork chops with remaining 1 1/2 tbsp. oil, then with coriander mixture. Taste chutney and add more sugar if you like.
Grill meat covered, turning over once, until barely pink in center, 12 to 15 minutes. Transfer to a platter. Stir cilantro into chutney. Set pork chops on plates and spoon chutney and juices on top.
*Crush seeds with a mortar and pestle, or seal in a plastic bag and hit with a rolling pin.