Хост - Win7
Гостевая - Linux deos 5.0.4-zen1-1-zen #1 ZEN SMP PREEMPT Sat Mar 23 20:59:30 UTC 2019 x86_64 GNU/Linux

Xorg.0.log
[   573.836] (WW) Warning, couldn't open module vboxvideo
[   573.836] (EE) Failed to load module "vboxvideo" (module does not exist, 0)
[   573.839] (WW) Falling back to old probe method for fbdev

Установлены
virtualbox-guest-dkms 6.0.4-4
virtualbox-guest-utils 6.0.4-4