Take a look at this article https://discussions.apple.com/thread/253598128 I'm experiencing the same thing on MANY Big Sur Macs looking for the 11.6.3 update. In the Software Update pane of System Preferences, it just sits there searching for updates with the spinning gear. I let it sit for many hours and in one case I let it sit overnight with absolutely zero indication of it doing anything. When I run softwareupdate -l in Terminal, it just sits there looking for updates and it never finishes. It doesn't happen on every Mac. There are some Macs that have absolutely no problems whatsoever finding, downloading, or installing the update. The OS versions of Macs having this problem range from 11.6.0 through 11.6.2. All various hardware configurations. I've tried it from the LAN in the office and I've tried it from home networks. Numerous reboots have no effect. Is anyone else here in JamfNation experiencing this? if so, how are you handling it? Before the 11.6.3 update was made available, we never experienced this.
Solved
Big Sur 11.6.x software update hangs
Best answer by mark_mahabir
There’s been a bit of discussion about this on the MacAdmins Slack. I can reproduce the issue and running this command helped:
sudo launchctl kickstart -k system/com.apple.softwareupdated
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