Yeah, doesn't work on dedicated since the curator addons takes time and the tree isn't refreshed in the next frame. Looking at it now, I am unsure about if there is a good way to support ZGM missions.

Yeah, it's an issue that has troubled us a lot in the past.
It's far from perfect, but Achilles basically checked for the presence of ZGM and counted the entries in the module tree.
Adapting this approach to unscheduled environment might be the best approach:

sleep 0.001;
// For Zeus Game Master missions: Wait until respawn was placed
if (!(missionNamespace getVariable ["BIS_moduleMPTypeGameMaster_init", false]) && {count allMissionObjects "ModuleMPTypeGameMaster_F" > 0}) then
{
    waitUntil {sleep 0.1; _moduleTreeCtrl tvCount [] > 1 || isNull findDisplay IDD_RSCDISPLAYCURATOR};
};
if (isNull findDisplay IDD_RSCDISPLAYCURATOR) exitWith {};

// wait for the next frame
sleep 0.001;
[Achilles_fnc_onModuleTreeLoad, []] call CBA_fnc_directCall;

If I remember correctly BIS_moduleMPTypeGameMaster_init gets set to true by the ZGM module when the respawn is placed, but due to race conditions, you still have to check the number of entries in the module tree.

I'm also not sure if both "delay by one frame with sleep 0.001" are really necessary. I might have just tested everything possible and left some unnecessary stuff around.

I can confirm that it works now for dedicated servers too.