[OnePlus 8 Guides, News, & Discussion] UniX1rm:
*** Use this at your very own risk.

***Backup your persist.img. There is a guide to fix it if needed.

*** Backup your working modem. Sometimes it is as simple as restoring it if you lose signal.

*** When flashing, you must understand the difference between fastboot and fastbootd to avoid flashing errors.

*** Backup your files in a safe place.

*** Some users are reporting that the whole thing is not working and going on a blame streak. So if you're not quite ready, please don't attempt this.

Basic Instructions: "I will test again since some users are losing signal after flashing". There is a debate whether msm and update the tmobile firmware, or flash the global. Again this is a WIP.

MSM. Here is the thread.

Unlock bootloader or re-unlock bootloader ... Enable OEM Unlock in developer options. flash token.

Fastboot

fastboot flash cust-unlock <unlock_token.bin>

fastboot oem unlock

and now your bootloader is unlocked.

Here is the t-mobile article for the 6t. same instructions for the 8 if you're new to this.

NEXT:

Link to fastboot thread

https://xdaforums.com/oneplus-8/how-to/rom-stock-fastboot-roms-oneplus-8-t4084629

Download the global fastboot rom from here.

Unzip and flash all.

Link to twrp thread:

https://xdaforums.com/oneplus-8/development/recovery-unofficial-twrp-oneplus-8-t4101315

If you want to root.

Boot into twrp or flash the twrp installer. TWRP 3.3.1-10 Test by mauronofrio and or TWRP 3.3.1-10 Test Installer by mauronofrio "newer ones may work"

After booting, you can flash magisk with-in twrp and you're rooted.

I have used oxygen updater to update the firmware while rooted. After the local install, open magisk and flash on the inactive slot.

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If you ever want to revert, use the msm tool. Here is the thread.

https://xdaforums.com/oneplus-8/how-to/op8-unbrick-tool-to-restore-device-to-t4093043

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Old information from the old thread is below, if you want to use it only for reference or for backing up the FP persist

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Old Instructions

Here we go .....

This is fairly new and hasn't been tested so, proceed with caution. There are more knowledgable people here. This was just tested quick and it worked.

Requirements

1-Be on T-mobile firmware and update to the latest version. If you are bootloader unlocked, you mean not be able to take OTA's and you may need to reflash with MSM and update, then unlock the bootloader again. Thread Thanks [MENTION=8234677]Some_Random_Username[/MENTION]

2 - Unlock your bootloader.

3- --! IMPORTANT: Make a TWRP backup of your MODEM because we'll restore that later, why? because t-mobile sim doesn't work on the Global Modem. You can also back everything up in TWRP just in case.

If you have OTG, make the backup there so it is safe. You can restore the modem through TWRP with the OTG.

4-Backup your persist. Otherwise you may lose the fingerprint.

You'll need root.

adb shell

su

dd if=/dev/block/bootdevice/by-name/persist of=/sdcard/persist.img

Then

adb pull sdcard/persist.img

Then copy it from from Sdcard to a safe place

*** You may lose signal again if you update the global version. It is a WIP but keep your modem backed up!

With all the above:

It is simple. Download the global firmware and flash it through fastboot. Here is the thread

.. I tested with "10.5.5-GLOBAL-OnePlus8Oxygen_15.O.14" Thanks [MENTION=4712355]mauronofrio[/MENTION]

Reboot to fastboot

Unzip and flash-all

It will reboot to the global firmware. "Now you won't get cellphone signal"

Skip the setup and reboot to fastboot.

reboot to twrp, do not flash it.

fastboot boot twrp.img

link to twrp thread. . I used TWRP 3.3.1-2 Test by [MENTION=4712355]mauronofrio[/MENTION]

plug in the OTG or locate the backup and Restore the Modem" to get signal

Reboot and you'll have signal.

To root. you can flash the patched boot located in the sourceforge folder " Patched-Stock-Boot" on this thread

fastboot flash boot filename.img

You can also flash magisk in twrp. I prefer the patched boot.

Bonus: I am running the Nolimit magisk rom Thanks [MENTION=1030560]xXx[/MENTION]

https://xdaforums.com/oneplus-8-pro/development/magisk-rom-xxx-nolimits-11-0-speed-ram-t4088609

Thanks [MENTION=10284123]Some_Ghost[/MENTION] for testing.