I am aware of the issue but there isn’t an easy fix.
The root cause of this issue:
Whonix ™ Virtualization Platforms
This situation might improve some point in future as per:
VirtualBox Guest Additions being upstreamed to Linux kernel.org
Next (follow-up) issue: there are no VirtualBox 6.1 and VirtualBox 6.1 guest additions Debian packages for Debian buster. See:
Installing VirtualBox on Debian 10 / Debian buster / buster-backports / fasttrack - #6 by Patrick
And downloading from Debian sid and re-uploading to Whonix repository no longer possible due to dependency issues.
Compiling from source code also doesn’t work with my setup:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=942873
Whonix testers repository has VirtualBox and guest additions 6.0.14 but migrating packages to stable-proposed-packages and stable repositories is a slow process since the tool chain is underdeveloped. Help welcome. Some starters: