I am currently using Ubuntu 16.04 in VirtualBox version 6.0.14 (macOS host). It works perfectly well with the VBoxVGA graphics controller and 3D acceleration enabled.
If I change the graphics controller to VMSVGA then performance becomes very bad. It significantly affects usability. If I change it to VBoxSVGA, it becomes literally unusably slow.
VirtualBox 6.1 has dropped support for VBoxVGA (VMSVGA is the recommended choice for Linux guests). If I upgrade VirtualBox to 6.1 I will not be able to use VBoxVGA anymore. Is there a way to make this version of Ubuntu run with reasonable performance with the VMSVGA graphics controller?
In VirtualBox 6.1.10, the performance with VMSVGA is still so bad as to make the system unusable.