@olivierlambert Hello
Yes, the problem is on http://mirrors.xcp-ng.org/8/8.2/base/x86_64/repodata/repomd.xml, there is 302 Found to non-IPv6 urls

You can try with :

curl -IvL http://mirrors.xcp-ng.org/8/8.2/base/x86_64/repodata/repomd.xml

You will see the differents mirrors associated (Link), and some of them redirect to ipv4.

< Link: <https://xcpng-mirror.as208069.net/8/8.2/base/x86_64/repodata/repomd.xml>; rel=duplicate; pri=1; geo=fr
Link: <https://xcpng-mirror.as208069.net/8/8.2/base/x86_64/repodata/repomd.xml>; rel=duplicate; pri=1; geo=fr
< Link: <https://mirror.as50046.net/xcp-ng/8/8.2/base/x86_64/repodata/repomd.xml>; rel=duplicate; pri=2; geo=fr
Link: <https://mirror.as50046.net/xcp-ng/8/8.2/base/x86_64/repodata/repomd.xml>; rel=duplicate; pri=2; geo=fr
< Link: <https://mirror-xcpng.torontot.fr/8/8.2/base/x86_64/repodata/repomd.xml>; rel=duplicate; pri=3; geo=fr
Link: <https://mirror-xcpng.torontot.fr/8/8.2/base/x86_64/repodata/repomd.xml>; rel=duplicate; pri=3; geo=fr
< Link: <https://updates.xcp-ng.org/8/8.2/base/x86_64/repodata/repomd.xml>; rel=duplicate; pri=4; geo=fr
Link: <https://updates.xcp-ng.org/8/8.2/base/x86_64/repodata/repomd.xml>; rel=duplicate; pri=4; geo=fr
< Location: https://rg2-xcpng-mirror.reptigo.fr/8/8.2/base/x86_64/repodata/repomd.xml
Location: https://rg2-xcpng-mirror.reptigo.fr/8/8.2/base/x86_64/repodata/repomd.xml
...
couldn't connect to host at rg2-xcpng-mirror.reptigo.fr:443:
 Failed to connect to 45.152.69.252

Thanks for your work !
I'm little new in xcp-ng, I was on xen few year ago.

I'm trying xcp-ng with an ipv6 only server.
ISO file is Ok for install.
Just a little thing, mirrors of packages don't all have an ipv6 record, and on a ipv6 installation I have some error.

I just change the file /etc/yum.repos.d/xcp-ng.repo :
Before :

...
baseurl=http://mirrors.xcp-ng.org/8/8.2/base/x86_64/ http://updates.xcp-ng.org/8/8.2/base/x86_64/
...

After :

...
baseurl=https://updates.xcp-ng.org/8/8.2/base/x86_64/
...

Regards