Yesterday, git.savannah.gnu.org was down due to a ddos. I had just completed a fresh install of guix as a system and could not guix pull because it could not be reached.
Any mirrors that can be used in these cases or do fresh installs just have to deal with it?
I can suggest that you define your own channels.scm. For example,
;;;; ~/.config/guix/channels.scm
;;;; https://guix.gnu.org/cookbook/en/html_node/Channels.html
;;;; https://gitlab.inria.fr/guix-hpc/website/-/blob/master/channels.scm
You can try the officially managed Codeberg mirror.
To add context: Migrating to Codeberg — 2025 — Blog — GNU Guix