Thanks again Aravisian. I will try your suggestions.
Prior to seeing your reply I had already ran
sudo apt install debsums
Then I checked the configuration files with
sudo debsums -sa
The above command found issues with libvirt and qemu-kvm packages that were installed the alongside MacOS kvm. I guess when I removed the MacOS kvm I needed to remove the qemu/libvirt packages that were left hanging around
I ran this command
sudo apt remove qemu-kvm libvirt-daemon-system
which successfully removed qemu and libvirt packages
Do you want to continue? [Y/n] Y
(Reading database ... 316838 files and directories currently installed.)
Removing libvirt-daemon-system (6.0.0-0ubuntu8.12) ...
Removing libvirt-daemon dnsmasq configuration
Removing qemu-kvm (1:4.2-3ubuntu6.17) ...
I will run your commands next to confirm that everything has been tidied up nicely.
You may consider using different File Manager as another option, too. I use Nemo File Manager as it restores a lot of functionality. You can also "minimalist" it, using the built in options to make it look a lot like Nautilus.