Sideloaded apps are apps added via a third-party mobile device management (MDM) tool or USB cable. By default, these apps do not appear in-headset, but you can configure this setting in Device Manager.
To enable sideloaded apps:
From Device Manager, click Device Fleet.
Click on the headset or group of headsets you want to enable sideloaded apps for, then click Settings.
Click next to Sideloaded Apps, then select On.
Review the Sideloaded Apps Warning, then click Turn on Sideloaded Apps.
Sideloaded apps will now appear in the selected headsets.