I had a working 16.04 working perfectly (but no bumblebee) and then upgraded to 18.04. Gnome was very laggy so I installed Unity and lightdm but it was still laggy. So I thought something was wrong with video drivers. So I purged nvidia and installed nvidia-driver-390, but I also tried to install bumblebee.
Then I reboot and startup stops with a PKCS#7 signature not signed error. I got into recovery console and removed nvidia-driver-390, but I'm still getting that same error. Had trouble enabling networking, as it would just hang and not return to recovery menu.
Any ideas what's wrong and how I can fix it? I'm thinking about running Nvidia binary installs but my home directory was encrypted and I had to give up last night. Anything else I can do?