Steps that I followed

Ensure that USB Debugging is turned ON . In fact, make sure it's always on during this entire procedure, because it's required. Enter fastboot mode via holding the power and volume DOWN buttons during boot up. Or easiest way is to simply soft reboot with the "Advanced reboot" option enabled from the Developer Options. Once in fastboot mode, enter the following command to obtain this 64 character code...

fastboot oem get_unlock_code

This will spit out that 64 character code. Now go to this page, sign in, and fill out the form to submit for the .bin file.

NOTE : This takes at LEAST 7 days to get the .bin file. For whatever reason...it must be an automated system. I tried contacting them twice, but they wouldn't budge and told me I had to wait. LOL. And it seriously took EXACTLY 7 days and like 12 minutes for the email to arrive.

fastboot flash cust-unlock "%path\to\unlock_code.bin%"

fastboot oem unlock

fastboot boot "%path\to\twrp-3.3.1-5-hotdog-unified-mauronofrio.img%"

adb shell dd if=/dev/block/bootdevice/by-name/boot of=boot.img

adb pull /boot.img

fastboot boot "%path\to\magisk_patched.img%"

fastboot --set-active=a

fastboot --set-active=b

Hi. So I wanted to put together a little write-up on how to root the T-Mobile McLaren 5G variant, at least how I rooted mine, as there doesn't seem to be anything about this yet. I was actually able to root my device last night successfully, so I hope this guide helps others go through the process.**WARNING** Unlocking your bootloader will render your phone unable to take OTA updates! This is a newly discovered problem that hopefully will be fixed soon. But currently, unlocking the bootloader will wipe your data and also a reserve.img needed for the OTA updates. Proceed with caution!*I do not take ANY credit for this work. I am simply gathering data from various sources into one single reference guide**Credit is due toandmostly, as I gathered most of the data from these members. Also,of course for Magisk.*So, anyhow, with this version of the OnePlus Pro 7T being carrier-locked, you must of course follow different procedures than a typical unlocked phone. And because OnePlus thinks they are special somehow, you also have to obtain an unlock code for the bootloader.1. Obtain SIM unlock status via T-Mobile. In order to do this, I simply just asked a T-Mobile employee via Twitter if they could provide me a permanent unlock. And without any issues, they were very kind to do so....even after day 2 of owning the phone. And on the EIP, it's not paid off.2. After getting them to add your IMEI to the unlock list, go to the system settings --> WiFi & internet --> SIM & network section. There will be an option called "Network Unlock" at the very bottom under the 'Advanced' section. Click that and then go through the prompts. You want to choose "Permanent Unlock". Then, if T-Mobile made on their promise, it should ask to reboot...after which the 'OEM unlocking' option under the Developer Options will no longer be grayed out. Woohoo!3. After obtaining successfulunlock, now you have to submit a form to OnePlus to obtain the actual unlock.bin file to get theunlocked, generated from a unique 64 character code you will obtain in the next step.4. So after you have the "key" to finally unlock this darn phone, enter fastboot mode again and enter the following commands...<here . To be honest, I am not even sure if using TWRP for this part is really necessary, but somehow I came to that conclusion. LOL. This process worked for me, so yeah. Anyhow, enter fastboot mode again andto TWRP (do NOT flash it!) by entering the following...Now in TWRP, enter the following commands to extract your stock boot.img file...This will copy your boot.img file to wherever adb is running on your computer.6. Take that boot.img file and copy it over to your internal SD on your phone. Boot your phone up as normal, and go grab Magisk Manager from Git here . Open up Magisk Manager, expand the "Advanced Settings" option, and check the "" and "". Select the "Install" button from the regular Magisk option and choose "". Find your boot.img file and Magisk Manager will created a patched .img file. Copy this new .img file from your phone over to your PC.7. Enter fastboot mode again. Now just boot from this newly patched .img file by entering the following...8. Final step. And hopefully your phone boots up.*If not, and you're stuck in a boot loop...you might need to make the A or B partition active. To do this, while back in fastboot mode, enter either command (most likely B)...Again, hopefully the phone just booted up normally without having to do that. Now in your phone, open up Magisk Manager again and simply choose the same Install option, but instead select "". Magisk will now flash that .img file, ultimately granting permanent root privileges.Reboot and enjoy!!***Here is a good write up on adb and how to get it running on your PC.... https://www.xda-developers.com/insta...s-macos-linux/ ***