For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:TruckerZer0/openSUSE_Tumbleweed/home:TruckerZer0.repo
zypper refresh
zypper install weechat
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:TruckerZer0/15.5/home:TruckerZer0.repo
zypper refresh
zypper install weechat
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:TruckerZer0/15.4/home:TruckerZer0.repo
zypper refresh
zypper install weechat