As pointed out by @job, docker.io/rockylinux/rockylinux:9 doesn't ship yum currently. After talking to Rocky Linux folks, it seems to be accidentially caused when updating the docker image to Rocky Linux 9.4 after switching from imagefactory to kiwi as image builder. Given we still support CentOS 7 (which reaches EOL at 2024-06-30), I added a not so nice workaround for the next two months. After EOL of CentOS 7, I will suggest to switch from yum to dnf, because yum is anyway just a wrapper to dnf since RHEL/CentOS/Rocky Linux 8 (and in Fedora even longer).
As pointed out by @job,
docker.io/rockylinux/rockylinux:9doesn't shipyumcurrently. After talking to Rocky Linux folks, it seems to be accidentially caused when updating the docker image to Rocky Linux 9.4 after switching from imagefactory to kiwi as image builder. Given we still support CentOS 7 (which reaches EOL at 2024-06-30), I added a not so nice workaround for the next two months. After EOL of CentOS 7, I will suggest to switch fromyumtodnf, becauseyumis anyway just a wrapper todnfsince RHEL/CentOS/Rocky Linux 8 (and in Fedora even longer).