I've installed Big Sur last night and got the same issue and RESOLVED it today morning.
What i did: Reboot laptop with Shift key to open Soft Mode.
Checked if internet is working through this mode - WORKS
Reboot laptop again without Shift key - EVERYTHING WORKS FINE.
Hope this will help you guys! Cheers
Butakov
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution