1. 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.
2. 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.
3. 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.
4. 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.