Currently Eluna can not interact with map data which are not scripted in Eluna. These restrictions should be removed and methods like Set/GetBossState should be exposed.
For example this adjustment can remove some restrictions:
https://github.com/azerothcore/mod-eluna/blob/e67a18ca7253dffa505c5f400c883165f6d10bef/src/LuaEngine/MapMethods.h#L315
int SaveInstanceData(lua_State* /*L*/, Map* map)
{
if (InstanceMap* inst = map->ToInstanceMap())
if (InstanceScript* script = inst->GetInstanceScript())
script->SaveToDB();
return 0;
}
Thanks @Nyeriah for the help with this issue.