I am having the same problem and its a massive issue. I have an aim training island that is designed to be a private experience where 4 players can lobby up and start the game. Instead, now there is no such thing as setting a island to private only, so by default all players who load into my game for the first time are loaded in to a public lobby.
This compeletely ruins the aim training experience because there are people who just load up on boogie bombs, bunkers, etc and as soon as you load in they boogie bomb you and kill you. They also bunker off all of the aim training scenario selections, etc. For whatever reason kids seem to enjoy this a lot, so its almost guaranteed to have it happen everytime you load into a game.
I REALLY would like to be able to make my map private-only again, but the best you can do is set to “party choice” for island matchmaking without breaking your map entirely it seems… when I set to private only it gives a matchmaking error everytime.
Publishing a map in ‘Private Only’ mode doesn’t function correctly, it behaves as if it were in public matchmaking. Currently, the only solution is to set the map to ‘Public and Private’ mode, so players can manually select the private option.