For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Virtualization:Staging:TDX/openSUSE_Tumbleweed/Virtualization:Staging:TDX.repo
zypper refresh
zypper install qemu-guest-agent
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Virtualization:Staging:TDX/15.6/Virtualization:Staging:TDX.repo
zypper refresh
zypper install qemu-guest-agent
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Virtualization:Staging:TDX/15.5/Virtualization:Staging:TDX.repo
zypper refresh
zypper install qemu-guest-agent