Hi @j_a_z_z,
I believe this is the correct callback for what you are trying to achieve. You can query the ZoomSDKBOMeetingAttendee object upon receiving this callback for the name of the breakout room to verify that you have been added to one. That same object can be used to join the breakout room.
Please let me know if I am misunderstanding and there is something more specific you are looking for which this callback does not accomplish.
Thanks!