Dear @olin,
The error “Status code: 404…” comes from a wrong repository address; my bad I gave you the wrong one for citrine depend! Please rectify:
$ cat /etc/yum.repos.d/eos.repo
[eos-citrine]
name=EOS 4.0 Version
baseurl=https://storage-ci.web.cern.ch/storage-ci/eos/citrine/tag/fc-31/x86_64/
gpgcheck=0
enabled=1
[eos-citrine-dep]
name=EOS 4.0 Dependencies
baseurl=https://storage-ci.web.cern.ch/storage-ci/eos/citrine-depend/fc-31/x86_64/
gpgcheck=0
enabled=1
`
The “Repository listed more than once…” is not a problem per se, but it comes necessarily from a double listing indeed; if you want to get rid of it, for example you may edit the headers [eos-citrine] and [eos-citrine-dep by appending a 30 in the .repo file, e.g.
$ cat /etc/yum.repos.d/eos30.repo
[eos-citrine30]
name=EOS 4.0 Version
baseurl=https://storage-ci.web.cern.ch/storage-ci/eos/citrine/tag/fc-30/x86_64/
gpgcheck=0
enabled=1
[eos-citrine-dep30]
name=EOS 4.0 Dependencies
baseurl=https://storage-ci.web.cern.ch/storage-ci/eos/citrine-depend/fc-30/x86_64/
gpgcheck=0
enabled=1
Nevertheless, you should not need these fc-30 repo and you can remove them safely.
Now the tricky part 
XRoot version 5.0.3 is a problem; xrootd version 4 and xrootd version 5 do not guarantee back/forw compatibility, and you need to uninstall it. EOS is at the moment still built with the latest stable xrootd4 version, which is thoroughly and extensively tested, and will step to xrootd 5 with a next major eos upgrade in the near future. But for the moment, please remove xrootd5.
You need to get xrootd-4.12.5 from the official Fedora31 repos. Here I provide you with a “quick and dirty” solution that I tried myself seemlessly on a container.
First create the content for fedora31 and fedora-updates31 repos,
$ sed "s/\$releasever/31/g" /etc/yum.repos.d/fedora.repo > /etc/yum.repos.d/fedora31.repo && sed -i "s/]/31]/g" /etc/yum.repos.d/fedora31.repo
$ sed "s/\$releasever/31/g" /etc/yum.repos.d/fedora-updates.repo > /etc/yum.repos.d/fedora-updates31.repo && sed -i "s/]/31]/g" /etc/yum.repos.d/fedora-updates31.repo
Then, install your eos-client by temporarily disabling the current fedora and updates repos:
yum --disablerepo="fedora,updates" install eos-client eos-folly-2019.11.11.00 eos-folly-deps-2019.11.11.00
And that should do.
Once finished, you may want to remove such “patched” fedora31 repos as they should not serve any other purpose, and it is good you keep your system updated from the proper upstream references.
That said, to prevent uncontrolled updates of the {eos-client, eos-folly, eos-folly-deps, xrootd} rpms, you can versionlock them to the current version.
In the hope that this will be helpful,
Cheers,
Fabio
355)
