If you are having issues with dowloading macOS updates displayed under System Settings, you can use Terminal to do so. Recently, with the way downloading Public/Developer builds of macOS is handled, I've noticed that sometimes downloads won't start or feel unresponsive – especially on legacy sysems patched with OCLP.
Since Apple decided to place the link for donwlonading macOS Sequoia on top of the list (even if you have selected public/dev builds of macOS Sonoma) it might also be helpful to download the update you actualy want.
- Open Terminal
- Enter
sudo softwareupdate -i -a -R - Enter your Admin Password
- This will trigger downloading the latest update:
Once the download has started, it will be reflected in System Settings > Software Update.