Para 15.6 execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:ykoba:Current_Leap/15.6/home:ykoba:Current_Leap.repo
zypper refresh
zypper install rust
Para 15.5 execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:ykoba:Current_Leap/15.5/home:ykoba:Current_Leap.repo
zypper refresh
zypper install rust
Para 15.4 execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:ykoba:Current_Leap/15.4/home:ykoba:Current_Leap.repo
zypper refresh
zypper install rust