The Apple way of solving this issue os the following:
– in Europe, they sell physical ISO extended keyboard, i.e. with that extra eleventh key left to W on the AZERTY keyboard (it is Z on a QWERTY keyboard, and Y on a QWERTZ keyboard).
– in U.S. they sell the standard American keyboard, without that key. In this case, what you have on that key on the EU ISO keyboard is moved to the key left to 1, i.e. the one having superscript 2 and 3 in your link; and that key vanishes.
That is why the char on that key is usually repeated somewhere else, i.e. superscript 2 and 3 should be available somewhere else if you press option = alt key.
Now, my question is: if you activate Keyboard Viewer, and press option = alt key, don’t you have all you need? Those chars should be on the key left to & and 1, even if not marked on the physical keyboard, but they are achieved when pressing that key. Give a try.