Google Home Integration - Just got my Hubitat

you should be able to still create an oauth on developers.nest.com

Login with your primary nest username
it will ask you to fill in a form/contact
when that is done, and you submit, scroll to bottom of next page and "create Oauth client"

In NST manager are the details for creating this. note you don't have to do all this with NST manager, but if you want your own clientID, then you can.