Expect longer downloads for updates, at least for Big Sur. Apple has stopped providing standalone installers (https://eclecticlight.co/2020/12/17/apple-has-stopped-providing-standalone-installers-for-macos-updates/)
Many versions still available at the Mac App Store (https://support.apple.com/en-us/HT211683)
These sites are the reason I looked into "Content Caching (https://techsurvivors.net/forums/index.php?topic=28845.0)" (thread here at TS) available in System Prefs."