So far so good, trying to simulate my actual system as much as possible, multilib minus the NVIDIA - and so far MATE1.18 works just fine under my virtual Slack VM
However while messing with the themes and settings, now for some reason I cannot click on anything but what is only on the desktop. I thought maybe I had messed something up with virtualbox, but no issue with mouse integration...
It resolved itself as soon as I exited and came back into MATE - I could then finally click on the items up on the taskbar this time. Again I don't know if that is really MATE or Virtualbox being dumb, but overall I like it so far.
Got GNOME Terminal the way I like it, and also GParted installed - can't live without the transparency effects
More transparency, and testing Audacity