Hi,
I also used he FP2 and the camera button does nothing currently. I see that there is a proposed enhancement here:
https://github.com/ubports/ubuntu-touch/issues/33
I like the idea to have this button configurable.
But it seems to not be a priority, and I agree with that, I would prefer to have first the camera flash working (see https://github.com/ubports/ubuntu-touch/issues/448).