I did this, and didn’t notice that for some reason apt decided qemu packages were autoremoveable and so accidentally uninstalled qemu packages.
When I realised this, reinstalled qemu and tried to start VM instances, this failed with a permissions error.
Could not open ‘/usr/share/OVMF/OVMF_CODE_4M.ms.fd’: Permission denied
I found this post and was able to get things going again.