For radio triggers, thisList (or list thisTrigger) always returns an empty array, making it impossible to find out who activated the trigger.
I'm not even sure I like the fact that it was changed to activate on all machines.
I had to create the trigger manually on each client to get it to not synchronize, and provide a way to detect who triggered it.
_trigger = createTrigger ["EmptyDetector", [0,0,0]];
_trigger setTriggerArea [0, 0, 0, false];
_trigger setTriggerActivation ["ALPHA", "PRESENT", true];
_trigger setTriggerStatements ["this", "SupplyDrops_Request = true", ""];
This makes it behave like it did in OFP, where it's only activated on machine of the player who actually activated it, and thus that machine can tell the server that its player wants a supply drop, or whatever.