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