All of the xlibre packages were removed.
I tried pkg upgrade -fy again, but it's the same result, where lightdm freezes up after starting.
Can you reproduce this problem on a test machine?
Upgrade from 14.3p0 to 14.3p2. There was never a 14.3p1, so far as I'm aware, maybe that caused a problem.
If the problem doesn't exist on a test machine with an intel gpu maybe I need to download the live installer. The one on the website is still 14.2p1.