Prior to 1.16, ender_pearls would collide with the end_gateway block. I could use this to determine where the end gateway is located when a player attempts to use one. However, it doesn't seem reasonably possible to get this information now.

Could an event be added that fires whenever an end gateway is used (a player throws an ender pearl into the end gateway), including that end gateway's location? It would be a plus to be regardless of whether or not the end gateway has an exit location set up, but being part of a teleport event (implying the end gateway has an exit location) would be fine too.