- Host: Kubuntu 18.04; Virtualbox v 6.1
- Guest: Clean install of neon 5.19 ; Display = VMSVGA

With 3d acceleration turned on, applications freeze for half a second or so when I launch them.
Switching between open windows seem to cause this short lag as well.
Behavior becomes normal again as soon as I turn the 3d acceleration off.

Does anyone know if I can fix this with my current setup?

Are the Guest Additions installed ?

Yes, virtualbox-guest-dkms, x11, and utils installed through repositories.

All guest additions features work correctly with or without 3d acceleration. Except maybe the full screen feature that I have to toggle manually, or I log into a black screen. But except this minor inconvenience, everything is working fine so far.

I read about people experiencing this kind of problem, and pointing at nvidia and fps settings or compositor back end here or here for example, but I do not understand much about drivers and graphics ...

I did try changing the compositor back end, I see no difference switching from open gl 2.0 (default) to 3.1, and xrender messes everything up as I expected.