For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:aburlakov:branches:openSUSE:Factory2/openSUSE_Tumbleweed/home:aburlakov:branches:openSUSE:Factory2.repo
zypper refresh
zypper install ruby4.0
For 16.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:aburlakov:branches:openSUSE:Factory2/16.0/home:aburlakov:branches:openSUSE:Factory2.repo
zypper refresh
zypper install ruby4.0
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:aburlakov:branches:openSUSE:Factory2/15.6/home:aburlakov:branches:openSUSE:Factory2.repo
zypper refresh
zypper install ruby4.0