I am part of cohort 3 and setting up on Mac OS also (Big Sur); I am following the notes here:https://docs.plutus-community.com/docs/setup/MacOS.html
Was able to complete Step 9 (build library). But on Step 10 I get this error: attribute 'plutus-playground' in selection path 'plutus-playground.client' not found
I tried suggestions in other threads (such as edits to nix.conf). And continuing to fishing around. Meanwhile trying to see if anyone else crossed this chasm....