I was able to install the latest redstone build (14393.3) on my Verizon M8 and its working out suprisingly well for this being an unsupported device. I've posted instructions on how to do this below.
NOTE: THIS PHONE IS NOT OFFICIALLY SUPPORTED BY THE REDSTONE BUILDS. I HAVE ONLY TESTED THIS USING BUILD 14393.3 ON THE INSIDER FAST RING. MY PHONE IS RUNNING ON VERIZON WIRELESS, THIS MAY OR MAY NOT WORK ON TMOBILE/AT&T/OTHER CARRIERS. I AM NOT RESPONSIBLE IF YOU BRICK/DAMAGE YOUR PHONE OR LOSE YOUR DATA. BACKUP EVERYTHING BEFORE YOU TRY THIS. IF ANY OF THESE STEPS SEEM TOO COMPLICATED DO NOT CONTINUE!
IMPORTANT NOTICE AS OF JULY 24, 2016! MICROSOFT HAS REMOVED THIS DEVICE FROM ALL RINGS OF THE INSIDER PROGRAM. IF YOU RESTORE TO WINDOWS PHONE 8.1, YOU WILL NOT BE ABLE TO UPGRADE TO WINDOWS 10 AGAIN. I'M WORKING ON A TUTORIAL TO GET BACK TO WINDOWS 10, AND I WILL POST THIS ONCE AVAILABLE.
NOTE ON THE VERIZON MODEL: DO NOT HARD RESET AFTER THE UPGRADE! YOU WILL LOSE YOUR DATA AND MMS APN! - I'm going to reset mine to 8.1 and upgrade again, which should give me back data access. I've found Verizon APNs online, but I'm not sure if these will work or not- if I find out I will update this post.
If you're using a different carrier, your model numbers may be different- write them down somewhere as you will need them after you install the update. To install redstone, we're essentially going to change our phone's model number to a redstone supported model and then change it back after the update has installed. The Lumia 735 seems to work, so I'm going to use that model.
What you'll need:
- Interop Tools installed on your phone
- Windows Insider app
Modifying the registry:
- Open Interop Tools (Settings->Extras)
- Click the "Registry Browser" button
- Open "HKEY_LOCAL_MACHINE"
- Open "SYSTEM"
- Open "Platform"
- Open "DeviceTargetingInfo"
- Open "PhoneManufacturer"
- In the "Value Data" field, enter "NOKIA" (all caps). Click "Write"
- Open "PhoneManufacturerModelName"
- In the "Value Data" field, enter "RM-1089_1087". Click "Write"
- Open "PhoneModelName"
- In the "Value Data" field, enter "Lumia 735". Click "Write"
Once you have modified the registry, open the Windows Insider app and join the fast ring. Reboot your device when prompted. After the reboot, check for updates and you should start downloading the latest redstone build. Once this has installed (it will take a while- took about 15 minutes on my phone) follow the steps below to restore your previous registry values- this seemed to fix some minor issues I noticed when using the phone after the update.
- Open Interop Tools (Settings->Extras)
- Click the "Registry Browser" button
- Open "HKEY_LOCAL_MACHINE"
- Open "SYSTEM"
- Open "Platform"
- Open "DeviceTargetingInfo"
- Open "PhoneManufacturer"
- In the "Value Data" field, enter "HTC" (all caps). Click "Write"
- Open "PhoneManufacturerModelName"
- In the "Value Data" field, enter "HTC6995LVW". Click "Write"
- Open "PhoneModelName"nice work
- In the "Value Data" field, enter "HTC6995LVW". Click "Write"