Microsoft recently issued documentation for redirect URL's to use the newer b2ctenantname.b2clogin.com URL instead of the login.microsoftonline.com which will eventually be depreciated.
https://learn.microsoft.com/en-us/azure/active-directory-b2c/b2clogin
I currently have an MS Dynamics 365 portal successfully set up to use Azure B2C which uses the microsoftonline.com URL as part of the login process.
Albeit, when I amend our dev environment to switch to the b2clogin.com URL's as documented, I see 404 errors.
After raising a call with Microsoft, I get this response; "I have confirmed with our Dynamics 365 team that since the login.microsoftonline.com is the link provided in the official Microsoft article, then probably the use of b2clogin.com hasn’t been implemented yet."
I'd like to reach out to the community and see if anyone else has successfully set up the b2clogin.com domain for the login process for the Dynamics 365 Portal before I continue troubleshooting?
While configuring MS Dynamics 365 to work with B2C (hope you only configured the system), you need to give authorize URL. URL looks like: https://login.microsoftonline.com/te/{Tenant}.onmicrosoft.com/oauth2/authresp
Now to make that support with b2clogin, you need to update the URL which you configured at MS Dynamics 365. URL looks like: https://your-tenant-name.b2clogin.com/your-tenant-name.onmicrosoft.com/oauth2/authresp