[OnePlus 6T  Guides, News, & Discussion] metaspook:
[IMG="OnePlus 6T OOS-10 TWRP-Root-Magisk from OOS-9"]https://i.imgur.com/QjGwTST.png[/IMG]

~This thread is also edits+mirrored on OnePlus forum by me ~
​

INTRO:

After long research and applying various technics I've successfully discovered several methods and made this guide for TWRP, Root and Magisk installation for OOS 9.0.17 to OOS 10.0 for Un/Rooted OnePlus 6T (fajita) device.

NOTES:

* How to Unlock Bootloader / adb sideload / Advanced reboots etc. This Link

* Methods are well tested read/follow carefully, retry or if bricked use Unbrick Tool

* To upgrade "OOS-9" to "OOS-10" u gotta be on "OOS 9.0.17" and "Method-3" is applicable for OOS 10.0+ OTAs

* Remember "Bootloader" is "Fastboot" and OTA flash changes the A/B slot.

* [TWRP] Bootup Message >> [TICK] Never show.. > Swipe to Allow Mod.. || Reboot Message >> Untick all > Do Not Install

* This guide can be ported for OnePlus 6 users with proper credit.

FILE MAP:

~~ Download Magisk-v20.1+ version for "FILE-1" || TWRP 3.3.1-27+ version for "FILE-2, 3, 4" || "FILE-6" from Magisk Manager

FILE-1 = Magisk-v20.x.zip

FILE-2 = twrp-3.3.1-xx-fajita-installer-mauronofrio.zip (Use TWRP 3.3.1-27+ version.)

FILE-3 = twrp-3.3.1-xx-fajita-Pie-mauronofrio.img (Use TWRP 3.3.1-27+ version.)

FILE-4 = twrp-3.3.1-xx-fajita-Q-mauronofrio.img

FILE-5 = OnePlus6TOxygen_34_OTA_040_all_1910270448_OOS-10.0.zip

FILE-6 = TWRP_A_B_Retention_Script-Magisk.zip

METHODS:

~~ Read "NOTES" first ~~

~~~~~~~~~~~~~~~~~~~~~~~~ Method-1 ~~

OOS 9.0.17 [UNROOTED] to OOS 9.0.17 [ROOTED]

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~. *Step 4 is to Keep/Install TWRP.

1. Unlock Bootloader >> [Complete Setup wizard steps] >> Reboot to Bootloader

2. Fastboot >> Command: fastboot boot "FILE-3"

3. TWRP >> Advanced menu >> Install Recovery Ramdisk

4. TWRP >> Flash or adb sideload "FILE-1" >> Reboot to System

~~~~~~~~~~~~~~~~~~~~~ Method-2 ~~

OOS 9.0.17 [ROOTED] to OOS 10.0 [ROOTED]

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~. *Step 3A is to Keep TWRP and *Step 3B is to Install TWRP choose any and don't reboot.

1. Flash "FILE-5" via Local Updater [DON'T REBOOT]

2. Connect Internet >> Magisk Manager

3A. Magisk Manager >> Download>Install or Flash "FILE-6" as Module

3B. Magisk Manager >> Flash "FILE-2" as Module

4. Magisk Manager >> Beside "Magisk is up to date" > Install > Install > Install to inactive slot

5. Reboot

~~~~~~~~~~~~~~~~~~~~~~ Method-3 ~~

OOS 10.0 [UNROOTED] to OOS 10.0 [ROOTED]

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~. *Step 4 will boot into TWRP and *Step 7 is to Keep/Install TWRP

~. To Reset Rooted "OOS 10.x" go to TWRP >> Wipe > Swipe to Factory Reset > Steps 6 to 10

1. Unlock Bootloader >> [Skip Setup wizard steps] >> Reboot to Recovery (Stock Recovery)

2. Stock Recovery >> "Wipe data and cache" > "Erase everything" > Reboot to Bootloader

3. Fastboot >> Command: fastboot flash boot "FILE-4"

4. Fastboot >> START

5. TWRP >> Switch slot > Reboot to Recovery

6. TWRP >> Flash or adb sideload "FILE-5"

7. TWRP >> Flash or adb sideload "FILE-2"

8. TWRP >> Switch slot > Reboot to Recovery

9. TWRP >> Flash or adb sideload "FILE-1"

10. Reboot to System

Contributors:

metaspook

Special Thanks to...

[MENTION=4470081]topjohnwu[/MENTION] [MENTION=4544860]osm0sis[/MENTION] [MENTION=4712355]mauronofrio[/MENTION]