If you are looking to travel from Munich to Dubrovnik by bus, you can for sure do so, the easiest and most flexible way of travelling is to take a bus from Munich to Zagreb, as you can see here there are several departures between the cities, once arrived at the main bus station in Zagreb you take a domestic bus to Dubrovnik, these bus run quite frequent as you can see here. Please note that return tickets are discounted, you buy one of those if you are also travelling back. Direct buses between Munich and Dubrovnik (Buses where you can buy end to end ticket), has not be running constantly the last couple of year, but if there should be one running during summer season, it will be listed below no later then 1st of May.