One the best phones of last year, the OnePlus 6T marked a new chapter for the Chinese company. Part of the progress involved a deal with T-Mobile, which came with its pros and cons. Since it's a different SKU from the international dual-SIM variant (such as you'd buy straight from OnePlus), the Tmo version is excluded from things like the Open Beta program. But some savvy people over in the XDA forums figured out a way to rebrand the Tmo 6T to the international version without unlocking the bootloader.
If the significance of that is lost on you, don't worry. Simply put, the conversion/rebranding isn't the big accomplishment — you could do that with the bootloader unlocked. Rather, the truly impressive act is achieving this while bypassing the bootloader, meaning that you don't have to wait for a SIM unlock from T-Mobile nor sit for a week while you wait for the code from OnePlus. Once you've completed this process, you'll be running the same OxygenOS version as the international 6T – which includes support for HD DRM – and can even install the Open Betas.
The instructions clearly state that doing this will wipe your data, much like unlocking the bootloader would, so bear that in mind before continuing. I'll go ahead and outline the instructions given by AnonymousTipster, the one who is credited with discovering this workaround (with some help from users Dark Nightmare and iaTa).
- Download 6T MsmDownloadTool v4.0.58 (OOS v9.0.11) provided by @iaTa
- Download patched flasher tools here: https://drive.google.com/open?id=1dY...EBOjau1BRvtnJQ (the patches simply remove checks that allow all the images to be flashed on the phone, I've personally tested the "MsmDownloadTool V4.0_factory_patched.exe" but not the "MsmDownloadTool V4.0_factory_mcl_op1_patched.exe" variant. You can do a binary diff on the EXEs against the originals in case there's any issues with trust.
- Shut down your T-Mobile 6T completely
- Press and hold Volume Up and Volume down keys simultaneously
- With those two buttons held down, plug in your USB cord to your PC
- Ensure that the USB drivers for Qcom download mode are installed and working (available in the MSMDownloadTool thread)
- Extract the patched tools EXEs to the same directory as where you extracted the MSMDownloadTool
- Run "MsmDownloadTool V4.0_factory_patched.exe" (or the other one, if you're feeling adventurous)
- Click "Start" when you're ready to start patching the phone
- After about 5 minutes it will finish its job and reboot the phone
- Phone will boot normally, but no more T-Mobile logo, and instead there is the OxygenOS generic logo
- Now your T-Mobile 6T is now running identical software to the unlocked 6T sold directly by OnePlus, and running the latest software (OxygenOS 9.0.11 at the time of this writing). You can even participate in Open Betas if you'd like, and the "Local Upgrade" feature is now enabled and working.
As is usual with these sorts of things, you assume all responsibility for anything that goes wrong — since I don't personally have a T-Mobile 6T to test this for myself, I cannot personally (in good conscience) recommend this. However, from all appearances, it seems to be a safe and worthwhile process.
To make this even sweeter, AnonymousTipster says that this conversion allows for an immediate bootloader unlock with the normal fastboot command. Furthermore, you can put in a loaded dual-SIM tray and the phone will recognize both cards. That's pretty great, if you ask me. So if you own a T-Mobile OnePlus 6T and you're wanting a bit more control over it, here you go. Enjoy.