I am running Kubuntu 18.04 with an ASUS MB169B+ USB monitor. Every time I boot up with the monitor plugged in I get the "PKCS#7 signature not signed with a trusted key." message...sometimes it actually boots into Kubuntu but most of the time it just freezes there in the boot process and it can take like half an hour of me rebooting till it works.
I am using a laptop which has 2 graphics cards, an nVidia one and a intel one. I think that Kubuntu is using the nVidia one (I am using nvidia drivers and its working) but I think this might all work better if I make Kubuntu use the intel card? I'm just not sure how to go about switching?
I have seen the following: PKCS Signature error/warnings running dmesg on Ubuntu Mate 18.04 so please dont direct me there as it doesnt help / isnt the same issue...I just want to be able to boot into Kubuntu without having to sit at my computer for half an hour each time, rebooting till it works.