For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:markusd:samba:samba-4.21-related:samba-4.21-mit-fs/openSUSE_Tumbleweed/home:markusd:samba:samba-4.21-related:samba-4.21-mit-fs.repo
zypper refresh
zypper install chrony
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:markusd:samba:samba-4.21-related:samba-4.21-mit-fs/15.6/home:markusd:samba:samba-4.21-related:samba-4.21-mit-fs.repo
zypper refresh
zypper install chrony