SUMMARY
To set up an Office 365 (@whatever.onmicrosoft.com) Exchange account, there are lots of steps required that can and should be simplified. The account as itself works, but setting it up is unnecessarily complicated

OBSERVED RESULT (Steps to reproduce)
1. I select Preferences | Configure KMail.
2. I press on the Reception tab, "Add...", "Custom account".
3. Select "Akonadi Exchange EWS" resource, press Add.
4. On email name, I enter my email (for this case, emanriquez@galantia.onmicrosoft.com)
5. Select as authentication method "OAuth2 (Office 365)"
6. I disable "Server auto discovery"
7. Press the button: "Try to connect"
8. I get a dialog showing me the real Microsoft authentication (user + pass + Microsoft Authenticator)
9. I get a bogus error message showing me the resource is broken.
10. I press OK and my EWS mail starts working.
11. I press on the Sending tab, "Add...", "Custom account".
12. I select again the Akonadi Exchange EWS resource, and select as parent resource the resource I created before.

EXPECTED RESULT
1. I select Preferences | Add account.
2. I enter my mail, emanriquez@galantia.onmicrosoft.com
3. Password is disabled, I press "Next".
4. I get the dialog showing me the Microsoft authentication page.
5. I press "Exit" and everything is ready.

SOFTWARE/OS VERSIONS
KDE Plasma 6.0.1.