Put one of these lines in /etc/apk/repositories, replacing the main line of an official mirror:
https://cdn-origin.net/pub/alpine/v3.24/main/
https://cdn-origin.net/pub/alpine/v3.23/main/
Only main is carried; keep the community line on an official mirror.
Pulled from rsync.alpinelinux.org every six hours. Upstream's last-updated is copied next to the tree.
No rsync daemon, no FTP, no community/testing, no architectures other than x86_64, no release images.