Is there a way to "ping" the map to get the attention of other players?
Solution 1:
There is no way to ping the mini-map, however you can use the G key to drop your banner on the ground to direct other player's attention to somewhere specific on the screen
Solution 2:
You could also try the emotes "Follow" or "Help". I'm not sure how far away the voice can be heard but I believe it always writes out the text of the emote. Not as useful as a map ping would be, but at least it's only a single key bind press like dropping the banner.