I’m sure that you will encounter problems when you fire up your new Kubuntu 20.10 Desktop virtual machine under the impression things would work out fine with just giving the VM the ISO file with these additions.
The install process will most likely fail. This is due to some missing parts which have to be installed beforehand. Here are the necessary commands you may just copy’n paste.
But either enter sudo before each command or become root with sudo su:
sudo su (that's the easy way)
apt-get install gcc
apt-get install make
Now you may mount the ISO file with the additions and start
autorun.sh manually (as root). You find it here:
After that, the Auto-resize Guest Display option should work!
The ISO file can be found here: