Azure Active Directory B2B - Helping confused users login

We're using Azure AD B2B for a few bespoke applications (customer portals etc) with several hundred guest users from other directories, mostly non-tech staff from small businesses with outsourced IT. Generally it works great but we regularly receive queries from customers confused about similar things and would like to provide an FAQ. I'm referring to issues like:

unsure which login details to use, since they're unfamiliar with SSO and don't realise they can just use their own O365 / Microsoft accounts, which many already have
surprised/suspicious when our application asks them for permission to access their account
have set Outlook etc to remember their password, haven't had to use it in years and don't know what it is, and we can't reset it since the account is in their own directory

Not asking for help with the specific issues above, my question is about the best way to provide easy access to some kind of FAQ page during the AAD sign-in process. The issue is that once they start the process (which is the part they struggle with), they only get redirected back to the application upon successful auth, and Microsoft doesn't give much control over the UI.

A perfect solution would be to have an FAQ or help link on all the AAD sign-in pages, but I can't see any way to do this, even on our own company branded sign-in pages. The only relevant option is "Sign-in page text", which isn't really sufficient.

What's the best-practice way to help non-technical users with these kinds of problems? E.g. can we tell AAD to redirect to a help page after login failures?

Solution

There is no way to specify custom error messages or error pages for Azure AD B2B. It is possible if you are using Azure B2C. https://learn.microsoft.com/en-us/azure/active-directory-b2c/customize-ui-overview

Also, for B2B users, they will receive an email if they are invited to your tenant. So they will know which account to use to login.