For standard run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:lalala123/standard/home:lalala123.repo
zypper refresh
zypper install mono-complete
For snapshot run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:lalala123/snapshot/home:lalala123.repo
zypper refresh
zypper install mono-complete
For openSUSE Factory ARM run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:lalala123/openSUSE_Factory_ARM/home:lalala123.repo
zypper refresh
zypper install mono-complete
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:lalala123/15.6/home:lalala123.repo
zypper refresh
zypper install mono-complete