Blocking macOS 15 and later system updates is very simple. Just edit the /etc/hosts file and add the following domain names.
127.0.0.1 gdmf.apple.com
127.0.0.1 gg.apple.com
127.0.0.1 gs.apple.com
127.0.0.1 ig.apple.com
127.0.0.1 mesu.apple.com
127.0.0.1 skl.apple.com
127.0.0.1 swcdn.apple.com
127.0.0.1 swdist.apple.com
127.0.0.1 swdownload.apple.com
127.0.0.1 swscan.apple.com
127.0.0.1 xp.apple.com
The above domain names are from: 在企业网络上使用 Apple 产品 - 官方 Apple 支持 (中国)
After blocking, System Settings will still display update badges and red dots, which is very annoying to look at. All you need to do is switch the Beta update channel and then switch back, and the red dots will disappear. The final effect is shown below.
