Knife bootstrap error - Successful authentication but not authorized for this action

Well, this turned out to be pretty simple after all. From the terminal on the Chef server:

sudo chef-server-ctl org-user-add <org> <user> --admin

Docs - https://docs.chef.io/server_users.html

I was able to add myself to the admins group and handle other permission related task from there

The server-admins group means you have permission to create and modify orgs/users, for operations within a single org (like creating a new client during bootstrap) you need ACLs within that org. Generally you get this by being a member of the admins group in that org, but you can also assign yourself specific permissions manually.