I just used the in-app support and got this answer:
"Hi Kristian,
Good day. We recently rolled out the Edge Webview Integration.
When users tap a link in an email or event in Outlook, it will now open in an integrated Edge webview within Outlook, instead of launching the user's default web browser.
If a user needs to open a link in their browser he/she will need to click the link, then tap on the overflow menu at the bottom and choose "Open in Browser" (see attached)
If you want to have this disabled which is not possible at the moment,
I highly encourage you to please send a feature request to our development team:
Tap account's avatar at the upper left corner ➔ ❔ ➔ Suggest a Feature.
Your suggestions & ideas are important to us to help make Outlook better. 😊
Regards."