After upgrading (reinstalling) my Mac to Big Sur (11.0.1) my Mac because unusable. The Finder was slow, I couldn't explore files through a browser or navigate my folders.
After doing a lot of things I ended up fully removing iCloud from the System Preferences and the Finder went back to normal.
I'm posting this because I could not find anything specific to finder issues after upgrading to Big Sur but I suspect I won't be the only one facing this.
Go to System Preferences > Internet Accounts > iCloud (from the left menu) unmark "iCloud Drive" and "Photos".
