For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:tst/openSUSE_Tumbleweed/home:tst.repo
zypper refresh
zypper install libatomic
For openSUSE Slowroll run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:tst/openSUSE_Slowroll/home:tst.repo
zypper refresh
zypper install libatomic
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:tst/15.6/home:tst.repo
zypper refresh
zypper install libatomic