In order to help organizations in choosing right peripherals for Microsoft Teams, Microsoft has a peripherals certification program. The certified devices work with no extra configuration required, and offer call control with Microsoft Teams. Right now, Microsoft Teams certified audio peripherals require USB dongle to support call controls. Microsoft has now confirmed that Microsoft Teams will support call control with Bluetooth headsets and speakerphones in April 2022.
With the upcoming Microsoft Teams certified Bluetooth audio devices, you will be able to use device buttons to control call (answer, end, hold) without needing a USB dongle when connected to a Windows PC running Teams desktop app. We are not sure whether existing Bluetooth devices can add this functionality through a firmware update.
According to Microsoft, for many headsets and speakerphones, this call control feature will work without requiring any additional user action to enable other than pairing the Bluetooth headset or speakerphone with the Windows PC.
You can visit the Microsoft Teams certification page for information about devices tested to meet all certification criteria with native Bluetooth connections (w/o a USB dongle).