If you have low asteroid settings, you can have a map with no durantium, if you want to check add "-cheat" to the launch params, in-game press tilda, then "fow" and check if the rest of your map has the resource. If it doesn't, I'd say restart the map.....
If you'd like to conquer planets without invading, influence can take planets forcefully! But they could have the upgrade to make them immune to culture flipping.....
