Accessing an Organization's SharePoint App with Username/Password: Bypassing Integrated IdP

Hello everyone,

I have a question regarding access configurations for SharePoint within an organization that uses an integrated Identity Provider (IdP).

Is it possible to access an organization’s SharePoint app using only a username and password, bypassing the configured IdP for authentication? If so, under what circumstances or configurations could this happen, and are there ways to enforce IdP-based logins consistently?

Additionally, in cases where a username/password login is possible, could these accounts be considered local accounts within SharePoint or Azure AD? Or are there restrictions within Azure AD/SharePoint that prevent true local accounts from existing?

Any insights or recommendations on managing or restricting this type of access would be greatly appreciated!
Thank you