Update on this issue
The issue occured when the OpenSUSE firewall was enabled. When I disabled the firewall, internet access to virtual machines through the default network worked as normal again.
I’ve been having an issue with libvirt where the default “NAT” network does not provide internet access to virtual machines.
On any other machine I have used, I haven’t experienced this issue, I do not have any firewalls installed on this OpenSUSE Tumbleweed desktop and yet still this issue occurs.
I have been unable to find what is causing this issue, but will add here when I gain some clues.
I have tried to recreate this network with:
sudo virsh net-destroy default
sudo virsh net-define /usr/share/libvirt/networks/default.xml
But the issue with VM’s not having access to the internet is still present.