Thanks everyone - Got it solved.
It seems (per a reddit thread) that when I installed Atom from unitedrpms it overwrote the
installonlypkgs=kernel line in /etc/dnf/dnf.conf with installonlypkgs=electron thus
breaking things. I changed it to: installonlypkgs=kernel installonlypkg(kernel)
installonlypkg(kernel-module) installonlypkg(vm)
That resulted in a successful kernel install and 4.6.3 booted fine.