Dear Sebastian Möllmann,
Thank you for posting in the Microsoft community.
I understand that you've encountered problems when connecting your Outlook mailbox in the Mail for Android App. I'm happy to explain it to you.
Indeed, when connecting an Outlook mailbox in the Outlook APP on a computer, it will be configured as the Exchange protocol type. However, in fact, in mailbox applications other than the Outlook APP, currently none of them can support configuring an Outlook mailbox with the Exchange protocol.
The configuration solutions provided in the link you attached are for the settings of some enterprise/school accounts, where they host their domains in the Exchange server. While personal accounts are usually configured via this option using the IMAP protocol. I think this official document hasn't been updated for a long time, and I apologize for the misunderstandings it has caused you.
To sum up, although I know you don't want to use the outlook APP, if you don't use it, you won't be able to configure your Outlook mailbox using the Exchange protocol, and it will also be difficult to synchronize the calendar and contacts of your Outlook mailbox to other apps. This is due to the system design.
I hope I've explained this problem clearly to you. Thank you for taking the time to deal with this issue. Wish you and those around you a Happy New Year and all the best!
Best Regards,
Ulrica.W - MSFT | Microsoft Community Support Specialist