[Google Pixel 4 Guides, News, & Discussion] i5lee8bit:
READ THIS ENTIRE POST BEFORE PROCEEDING!

ADDITIONAL PRELIMINARY STEPS COMPARED TO PREVIOUS MONTHS - DO NOT SKIP!!!!:

A. Make sure all of your Magisk / EdXposed modules are updated for compatibility with R. For example:

* Magisk Module: Riru (Riru - Core) v21.3

* Magisk Module / EdXposed version: EdXposed v.0.5.0.6-android_r (4561) [this is a Canary build]

B. Recommend disabling any Magisk and/or Xposed modules that have not been tested with Android R.

C. Install latest Magisk Manager build: https://github.com/topjohnwu/Magisk/releases/download/manager-v8.0.2/MagiskManager-v8.0.2.apk

D. Regular reboot the phone to make sure updates are applied before proceeding with the rest of the update process.

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EASY UPDATE / SEAMLESS KEEP-ROOT UPDATE PROCESS

(using a PC - a very intuitive, effective, and relatively safe method).

** You can only follow this guide verbatim if coming

EXACTLY from build "10.0.0 (QQ3A.200805.001, Aug 2020)"

. But the general idea is the same for other builds, you just need the correct files for your device.

flame-qq3a.200805.001-factory-dtbo.img: https://www.androidfilehost.com/?fid=8889791610682911608

flame-qq3a.200805.001-factory-boot.img: https://www.androidfilehost.com/?fid=8889791610682911606

September 2020 sideload OTA zip: https://dl.google.com/dl/android/aosp/flame-ota-rp1a.200720.009-6dde3195.zip

DO NOT BOOT BACK INTO O/S UNTIL ALL STEPS ARE COMPLETED - THIS ENSURES EVERYTHING BOOTS BACK UP WITH MAGISK / EDXPOSED ALL RUNNING PROPERLY RIGHT AWAY

1. boot into bootloader

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** I was on custom kernel, so I needed to flash BOTH the stock boot and dtbo images

2. fastboot flash boot flame-qq3a.200805.001-factory-boot.img

3. fastboot flash dtbo flame-qq3a.200805.001-factory-dtbo.img

......* these steps to restore stock recovery; dtbo.img also necessary for some kernel installations.

......* won't hurt to flash both anyway, so if you're unsure, go ahead and do both.

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4. use volume keys to change selection to boot to Recovery Mode

......- when you reach the android symbol with No Command, hold power button, tap volume up, in case you've forgotten

5. choose option "Apply update from ADB"

6. adb sideload flame-ota-rp1a.200720.009-6dde3195.zip

7. Once the OTA sideload is done, Reboot to bootloader (you'll also notice it's now on the other slot after OTA flashed)

8. fastboot flash boot flame-rp1a.200720.009-magisk_patched-21.0.img

9. done, start the phone

(Optional - Flash custom kernel. If you had a custom kernel, you need to re-flash it)

This is a 100% seamless update that requires no additional / re-setup of any of my Magisk or EdXposed setups. All of the factory files can be found here https://developers.google.com/android/images. boot.img and dtbo.img are in their corresponding full Factory Image zips, and the ota zip is under Full OTA Images.

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ADDITIONAL NOTES FROM [MENTION=1607642]sidhaarthm[/MENTION], WHO TESTED FOR ME - THERE'S SOME GOOD INFO HERE TO HELP PREP YOU BEFORE UPDATING YOUR PHONE (NOTE, THIS WAS DONE BEFORE MAGISK MANAGER 8.0.x BECAME STABLE, AND WAS FOR PIXEL 4 XL):

Big thanks to [MENTION=1607642]sidhaarthm[/MENTION] for being an awesome and detailed tester!

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Issues after updating?

If you end up unable to boot or bootlooping afterwards, you most likely have an old Magisk module that isn't playing nice with the new build. There are 2 main things you can do:

1. Flash the new factory untouched boot image. You will of course lose root, and all modules will be disabled. However, it should at least get you able to boot back up quickly and have a working phone if you're in a bind.

2. I would recommend checking Tulsadiver's thread: https://xdaforums.com/pixel-4/how-to/magisk-modules-disabler-booting-magisk-t3991739

Instead of reverting to stock boot image, fastboot boot (NOT FLASH) Tulsadiver's boot image. This will boot your phone in Magisk Core-Only Mode, with all modules disabled but root retained. From here you can open Magisk Manager and disable suspect modules. Before rebooting, go to Magisk Manager's settings and disable Magisk Core-Only Mode. Once you disable the incompatible module, the phone should boot back up.

- See this post (or thread) for more tips / context / an example: https://xdaforums.com/showpost.php?p=82509691&postcount=16

Coming from an earlier build than August 2020?

Download the September 2020 Full Factory Image .zip file and extract it. BEFORE RUNNING THE FLASH-ALL BATCH / SHELL FILE, EDIT THE FILE AND REMOVE THE "-w" FLAG FROM THE LAST FASTBOOT LINE. If you fail to remove -w, your phone will be wiped when it reaches this step. After flashing the full factory image, your phone will automatically reboot into O/S. From here, reboot back into bootloader, and flash the new Magisk patched boot image.

Since this is a major jump to a new version of Android, I don't want to recommend this yet until someone tests it. If anybody tries this way successfully, please let me know so we can update this part. Thanks!