We’re still investigating what’s causing this, but recently Outlook started automatically adding a Teams link to all meetings you create in Outlook via Outlook for Mac (old or new), and Outlook Web Application (OWA). This is happening independent of whether you have specified “All meetings are online” in your preferences.
Until this is rectified, when you’re creating a new meeting, if you do not intend for it to be a Teams meeting, you will need to uncheck that option. In OWA and “New Outlook”, it’s a little slider in the “Location” area. In “Old Outlook”, it’s in the toolbar ribbon next to “Reply All”.
BIS is investigating.