Neutral and ground are not the same thing when it comes to safety. Never try to use one for the other.
As far as what you do when you don’t have a ground, I will leave that to the electrical experts to answer. Wiring code is different in different countries regarding this matter. In some set ups it is possible to ground a device to the metal pattress box but you really need to know what you’re doing to make that decision, and it still might not be to code. So again, I’ll leave the remainder of the discussion up to the electrical experts.
