Skype for Business is only showing a splash screen and then exits without any error message. VBox.log shows the following entry upon clicking the Skype icon:
00:01:32.384054 VMMDev: Guest Log: crUtil DLL loaded.
00:01:32.786791 VMMDev: Guest Log: OpenGL Warning: crPixelCopy3D: simply crMemcpy'ing from srcPtr to dstPtr
I am using the VBoxVGA driver (also tried SVGA but there are so many other graphical glitches/flickering it is unusable) and I also tried with and without 3D acceleration.
The only thing that works to make Skype run again is to deinstall the guest additions but then I have a very small resolution and can't work properly anymore as copy/paste does not work, no shares etc

Is there anything else I can try? Maybe a regression of this bug? #17092 (forum does not allow links on first day/post

HW: Thinkpad T470p, Ubuntu 18.04 LTS, Win10 Guest, no vbox extension pack
3D controller: NVIDIA Corporation GM108M [GeForce 940MX] (rev a2)
for the record, the daily testbuild of the guest additions does not work either (VBoxGuestAdditions_6.0.1-128063.iso)