I've found another convoluted way around this governed by my Company's Global IT obsession with making as much as possible an 'Admin' task.
Disabling the add-in through Outlook 2016 has no effect - reinstated every time - auto load on startup 'governed by organisation'.
The 'Auto add online meetings' option doesn't exist.
We have Zoom but enabling the Zoom-Outlook add-in is 'Admin' only.
The below to 'disable' the auto add for teams meetings only works if you do NOT have the Zoom meetings add-in installed.
So... login to Office 365 web (sorry).
- got to Outlook or Calendar and select the settings gear wheel in top right
- Choose 'Calendar' then 'Events and Invitations'
- Enable 'Add online meeting to all meetings'
- Set 'Meeting Provider' to Zoom
So I'm telling it to use Zoom, Zoom add-in in Outlook doesn't exist, so Outlook meetings does nothing.
So far this seems to be sticking despite performing a number of restarts to test.