Windows Insider app for mobile devices updated to allow enrolled phones to receive firmware updates. Up until now mobile devices registered to be part of the Windows Insider Program weren’t allowed to receive new firmware updates. These updates were only available for devices that were configured to download production updates.
Since the Insider program began, users wanting to get the latest firmware for their devices needed to roll back using the Windows Device Recovery Tool before trying to install a new firmware update on their Lumia 950, Lumia 950 XL, and other Windows 10 Mobile devices enrolled in the Insider program.
Install firmware update on Windows phones
Now the software maker is working on a solution to make it easier for Insiders to receive the firmware update without having to roll back. For now, there is a temporary workaround that Microsoft explains as follow:
Open the Windows Insider application on your device.
Select Get preview builds.
Select Production from the list of options.
Read the presented message and tap accept to confirm your selection.
Your device may prompt to reboot. If not, complete a manual reboot.
After the reboot, check for updates. If available, your device will display an update to receive the newest firmware.
Settings > Updates & security > Phone update > (check for updates). If the device shows a “no updates available” message, your device has the most recently available firmware
If available, complete the update by following the on-screen directions.
Once installed, re-open the Windows Insider application.
Select your desired update ring (Insider Fast or Insider Slow) and reboot as prompted.
Your device now has the newest firmware available and is set to receive the next flight when launched for your selected ring.
Microsoft notes that availability of firmware updates will depend upon country or particular mobile operator network, and some Windows 10 Mobile devices mobile devices with specific configurations may receive firmware updates at a later time.
Of course, this is just a temporary workaround, the company plans to fully integrate firmware updates in the Windows Insider Program without so much friction, but for now these instructions should do the trick.
Source Microsoft forum