There is a possible bug in Teams Mobile App at the moment – or perhaps this feature is intentional and coming to desktop apps later. What I recently discovered was that invited external user into Teams meeting and they join using mobile app they can start and stop recording – overriding host’s recording.
I tested this using a meeting where a user from another tenant was invited to. I was playing with mobile app at the moment and noticed that invited user was able to start the recording and usual recording notification alerts were shown. I assume you can do this only, if you are able to usually record a meeting in your own tenant.
The recording is stored to recording starter tenant’s Stream. So if I were to participate in any Teams meeting I could join in using mobile app and record it in my tenant’s Stream. The Meeting host (or any host’s tenant users) can stop this recording normally – and they get the alert too.
If the meeting host had started a recording, I also had the full control to stop their recording and start my own.
I was not able to do this using a desktop client, only when I was using the mobile app on Android. When tested with iPhone users they did not have the option to start or stop recording.