@ppgrootens
We had the same issue that was only affecting a small sub set of users. We finally pinpointed the issue and resolved it so hopefully this may help others.
For us, it was related to an Office Policy that someone created for testing purposes. They applied to an O365 group of about 10 users (few members of IT). When we looked in the policies prior there was nothing as they had applied the policy, applied some of the recommendations, and later deleted the policy. Although the policy was deleted the settings were still applied to these users M365 apps and thus causing the Meeting link formatting issue. Also, it was causing these users issue with the FindTime add-in and presenting them with an error that it 'could not insert find time where cursor was'.
If you login to Office Cloud Policy Service - Apps Admin Center, you can see if any policies exist. In our case none did but we were able to create a new one and apply to the same group.
When we did this, it brought back all the prior security recommendations that were applied.
We went through each one and told it to revoke the setting, thus having no policies applied.
Once the workstations synced, the users had to close all Office apps, relaunch and it fixed both the Teams meeting add-in formatting and the FindTime issue.
Hopefully this is helpful to others.
