Delete Edge, run outlook and set your preferred browser and it will stop. Microsoft will more than likely get slapped for this, just will take a while.
They want to force you to use edge.
Hey Kip,
Thank you for the tip. I have given this a try, however, sadly it has made no change.
Whenever I try to open an attachment from an email, it still only opens it in the preview window with the email on the side and not using the desktop app as the full release desktop Outlook does.
Looks like this is intentional and that they've decided to remove that feature for whatever reason from the pre-release outlook.
Whenever I go back to the desktop outlook it works fine using the desktop app to open attachments.