What is the ruling on delaying Maghrib prayer in Ramadan?

It's a good thing, and the Prophet ﷺ used to wait on his companions and did not make Iqama (the call to stand up to start prayer) until they broke their fast and could attend. Even when he was in ruku' (prostration in standing position) and heard the footsteps of people coming in, he wouldn’t raise his head so they would be able to do ruku' with him ﷺ.