There requires some code update but is quite trivial to do.
There was some confusion among the community with linking warnings but these just turned out to be user error.
The functions OnControllerButtonPressed/Released using FKey were deleted for 4.6. This leaves plugin authors no way of propagating key presses from their plugin in to the input system.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-6400 in the post.