Hi @tellison
If you are just using local logins for some people, they can always access local (non-SAML) credentials by going directly to the Canvas local login page at https:// [my canvas server] /login/canvas . Instructure refers to this as the "Login Release Valve" on the Google SAML config page https://community.canvaslms.com/t5/Canvas-Integration-Documents/Configuring-Google-SAML-and-Canvas-A...
You can actually have several different authentication providers, but if you want users to be able to pick which authentication provider to use when they go to Canvas, you will need a "discovery page", or else users will be taken to the first auth provider in the list by default, unless they know the URL for the specific auth provider login page they want to use.