Your issue is partly your phone's. On later Android devices, the requirement of giving "Nearby devices" permission is explicitly popped. It started late last year when this requirement was added by Teams.
Give it time... The issue will reappear. Enabling permission for "Nearby devices" does not solve the issue persistently. I am on Teams about 8 to 10 hours of a day, and this issue reappears randomly throughout the day. The solution mentioned to turn on BT accessory before the call also doesn't make technical sense - Android broadcast to all apps when new audio device is attached to the system... Also, not everyone has every BT accessory turned on, so you can turn it on after a call/meeting initiated, i.e., have multiple BT headsets and decided to change after call started. If "Option 2" works, it means it's an Teams app bug. If should respond to OS broadcast of new audio devices and re-enumerate its audio device/endpoint list.
This is a Teams app issue - absolutely NO other app has this issue. I am talking about Zoom doesn't have it, Meet doesn't have it, WebEx doesn't have it, GotoMeeting doesn't have it. Heck, even Microsoft's own Skype doesn't have it.