For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:R:autoCRAN/openSUSE_Tumbleweed/devel:languages:R:autoCRAN.repo
zypper refresh
zypper install R-rpart
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:R:autoCRAN/15.6/devel:languages:R:autoCRAN.repo
zypper refresh
zypper install R-rpart
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:R:autoCRAN/15.5/devel:languages:R:autoCRAN.repo
zypper refresh
zypper install R-rpart
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:R:autoCRAN/15.4/devel:languages:R:autoCRAN.repo
zypper refresh
zypper install R-rpart