When enabling the [rt] section in the configuration file /etc/yum.repos.d/rocky-addons.repo, if you use its default baseurl parameter, and comment out the mirrorlist parameter:
[rt]
name=Rocky Linux $releasever - Realtime
#mirrorlist=https://mirrors.rockylinux.org/mirrorlist?arch=$basearch&repo=RT-$releasever$rltype
baseurl=http://dl.rockylinux.org/$contentdir/$releasever/RT/$basearch/os/
gpgcheck=1
enabled=1
countme=1
metadata_expire=6h
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-Rocky-10
Executing dnf repoinfo results in an error:
# dnf repoinfo
Rocky Linux 10 - Realtime 898 B/s | 2.7 kB 00:03
Errors during downloading metadata for repository 'rt':
- Status code: 404 for http://dl.rockylinux.org/pub/rocky/10/RT/x86_64/os/repodata/144134e15bd9faa116fd232b199336302687a7950ac88f7a30a88fffa46fa841-primary.xml.gz (IP: 151.101.198.132)
Error: Failed to download metadata for repo 'rt': Yum repo downloading error: Downloading error(s): repodata/144134e15bd9faa116fd232b199336302687a7950ac88f7a30a88fffa46fa841-primary.xml.gz - Cannot download, all mirrors were already tried without success
Obviously, this is because the file specified in the configuration, repodata/144134e15bd9faa116fd232b199336302687a7950ac88f7a30a88fffa46fa841-primary.xml.gz, does not exist. The actual file present is:
https://dl.rockylinux.org/pub/rocky/10/RT/x86_64/os/repodata/dab272dba153d01c65c3ffc57ac69a5985871d570952c65b9fb3a9f1e62b0f2d-primary.xml.gz
<repomd xmlns="http://linux.duke.edu/metadata/repo" xmlns:rpm="http://linux.duke.edu/metadata/rpm">
<revision>10</revision>
<tags>
<distro cpeid="cpe:/o:rocky:rocky:10">Rocky Linux 10</distro>
</tags>
<data type="primary">
<checksum type="sha256">144134e15bd9faa116fd232b199336302687a7950ac88f7a30a88fffa46fa841</checksum>
<open-checksum type="sha256">08f336f26b2a11bb0a3b5f48423700bf3ac4bbd0f6bec171c05d3d9b07101967</open-checksum>
<location href="repodata/144134e15bd9faa116fd232b199336302687a7950ac88f7a30a88fffa46fa841-primary.xml.gz"/>
<timestamp>1778663171</timestamp>
<size>14052869</size>
<open-size>103386132</open-size>
</data>
...