After solving this and posting to AskDifferent.... I realized this is probably the case with any OS:
in my case I was using MacOS High Sierra 10.13.6 with new install of VSCode 1.50.0 (see screenshots below):
Scenario:
Attempt to "Sign-in to Sync Settings"
web/browser-based SSO redirects to Microsoft and/or Github browser login
login fails - error message in VSCode:
Error:
Writing login information to the keychain failed with error 'UNIX[No such file or directory]'.



