just want to make a note that after upgrading cloud recognition stopped working on some internal null pointer exception
NullReferenceException CloudRecoAbstractBehaviour.Start ()
there is no backrtrace at all.
It took me few hours fiddling with everything. Finally found by comparing sample cloud project little by little that new vuforia extention needs some script keep alive attached to camera even it does not define anything there. It just must be present.
I do not know when this was introduced but If this is so required feature now by 2.8 that all cloud reco should die because of it, it should be noted down to migration guide.