I had the problem of sometimes having to use an alternative XKB keyboard back in 12.04 Precise, but then I could simply choose my default keyboard.
In 16.04 Xenial, there seems to be the subtlety that the display says I have the first keyboard (the default UK English keyboard from XKB), but I suspect that that it is not the active keyboard. If IBus keyboard selection is working, switching applications throws me into my first IBus-dependent keyboard, which is not my default keyboard, but the keyboard indicator shows my default keyboard, the XKB UK English keyboard. Attempting to use the US English keyboard does not work.
I use a variant of orange-buffalo's solution of 2016-12-13. I switch to an unpassworded account and then switch back to my account. As my password is accepted, a message flashes up in red which appears to say that my password is invalid. However, it is too fast for to me read it accurately.
I had the problem of sometimes having to use an alternative XKB keyboard back in 12.04 Precise, but then I could simply choose my default keyboard.
In 16.04 Xenial, there seems to be the subtlety that the display says I have the first keyboard (the default UK English keyboard from XKB), but I suspect that that it is not the active keyboard. If IBus keyboard selection is working, switching applications throws me into my first IBus-dependent keyboard, which is not my default keyboard, but the keyboard indicator shows my default keyboard, the XKB UK English keyboard. Attempting to use the US English keyboard does not work.
I use a variant of orange-buffalo's solution of 2016-12-13. I switch to an unpassworded account and then switch back to my account. As my password is accepted, a message flashes up in red which appears to say that my password is invalid. However, it is too fast for to me read it accurately.