When checking repoclosure in packaging we’re using the repository at http://mirrorlist.centos.org/?release=8&arch=x86_64&repo=configmanagement-ansible-29.
When you install centos-release-ansible-29 on EL8 it will set things up for you to be able to pull ansible from there. This should probably be mentioned in the docs and maybe the installer should be able to deal with it?