For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/server:irc/openSUSE_Tumbleweed/server:irc.repo
zypper refresh
zypper install weechat
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/server:irc/15.6/server:irc.repo
zypper refresh
zypper install weechat
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/server:irc/15.5/server:irc.repo
zypper refresh
zypper install weechat