[Miscellaneous Android Development] _cab13_:
Welcome to this guide, where I will guide you through rooting, flashing custom roms, and more, on our little Umidigi One Max !

WARNING : I am not responsible for your phone breaking or exploding during the night under your pillow. Please advice. If you cannot boot anymore, keep reading, your phone is NOT dead.

OFFICIAL ROM (Android 8.1)

The Umidigi One Max comes with Android 8.1 Out of the Box. Manufacturer has no plan on having 9.0 on the phone. That's why we root then ! Let's get into it.

Rooting the phone without unlocking it, or installing TWRP

Everything you'll do on this phone will NOT require a bootloader unlock. Note that this method is only in case you don't want to have your data wiped, or don't have access to an SD card (thus you cannot flash .zip in TWRP, except for ADB Sideloads)

What you'll need

Download the latest ROM from Umidigi's website : https://community.umidigi.com/forum.php?mod=forumdisplay&fid=211

Choose the ".rar" file

"E" ROMs are for European versions. It doesn't really matter what you choose.

Download SP Flash Tool on the same thread you opened for the ROM. It's "SPFT" for short

Unzip both

Install Magisk Manager on your phone : https://github.com/topjohnwu/Magisk/releases/

Steps

IMAGE COURTESY OF bencebacsi @ Umidigi forums

In the unzipped ROM folder, find boot.img

Copy it to your phone storage using an USB cable or any other method

Open Magisk Manager, press install

Choose "patch boot image file"

Let magisk do it's job

Find the boot.img file you just copied

Copy the patched_boot.img back to your computer

Open SP Flash Tool

Open the "Download" tab

In "Scatter-loading file", press the folder icon and browse to the downloaded ROM folder. Choose the only file that shows up

Untick every box except for boot. There is a column called "Location" with a path, click on it to change to file.

Choose patched_boot.img

MAKE SURE YOU UNTICKED EVERYTHING EXCEPT BOOT

Click the "Download" button

Turn off your phone (not reboot) and connect is via USB

wait for the flash to succeed. Once done, unplug, boot, voila ! You got magisk !

Credits to topjohnwu for Magisk, what a great piece of work :)

Installing TWRP

Note that if you want to access the /data partition (internal storage), you'll have to wipe it ! If you do not need it, keep going, it won't wipe unless you want to.

What you'll need

Official TWRP recovery.img by chankruze : https://twrp.me/umidigi/onemax.html

Magisk.zip installer (NOT the manager) : https://github.com/topjohnwu/Magisk/releases/

SP Flash Tool : http://www.mediafire.com/file/wxlld9dfywk67jl/SP_Flash_Tool_v5.1916.rar/file

This method is shorter and requires less downloaded files.

Steps

Turn off your phone

Run SP Flash Tool

Load the scatter file (see pictures above) you downloaded from the latest ROM (see above as well)

Untick everything except recovery

Change path to recovery.img to be the TWRP image

Click "Download" and plug your phone

After it's done, unplug, and press Power + Vol Up

You'll see three options appearing. That's how you'll get to the recovery. Use Vol Up to scroll, and Vol Down to select. Choose Recovery Mode !

TWRP should boot by now

EXTRA STEP : Make /data readable. You will need to format data (YOU'LL LOSE ALL YOUR DATA) (Wipe > Format Data > Type "yes") and after that, flash this zip : https://androidfilehost.com/?fid=1322778262904004415

You can now proceed to flash zips, including Magisk.zip. If you made /data readable, you can send it to your internal storage. If not, use an SD CARD or ADB PUSH / SIDELOAD.

Returning to stock to fix issues / brick

Use SP Flash tool but instead of unticking everything, tick everything. Note that USERDATA, if ticked, will clear your data.

Ticking only certain partitions may work if you got issues with magisk or system mods and are still on Official ROM. Flashing boot and system will remove Magisk. If you are on custom ROM, you can flash their system again to fix issues as well. Make sure to choose the right system.img in SPFT !

OTHER ROMS

Installing GSI (Generic System Image) to get Android Pie 9.0

GSI takes advantage of Project Treble to create one system image that will work on most devices without issues due to a separate "vendor" partition. The One Max is Treble-compatible, but only up to 9.0 (No 10 Q for now)

This will allow you to get an AOSP experience, with it comes easy modding and theming, and less bugs, less chinese-spying (that's a thing apparently, but who cares really ? Not me to say the least)

GSI List

You can find a GSI List including bugs and download links in my other thread here : https://xdaforums.com/android/development/gsi-gsi-experiments-t3941194

WARNING : DOWNLOAD GSIs WHICH ARE ARM64-AONLY AND NOT AB !

Installing a GSI

You will need TWRP Installed. Check above if it's not done yet. You'll also need the Magisk.zip, and I highly recommend you getting the disable-force-encryption zip

Start up by wiping /data in twrp (Wipe > Swipe the bar). It will not wipe the files in your internal storage (Music, Download, etc...). If you want to get access to /data in TWRP (which I highly recommend), you'll need to do a full format (Wipe > Format data > type yes).

Download a GSI (.img) and send it to your phone (Either using an SD Card, or adb push [file on computer] [destination folder]). Send Magisk and the disable-force-encryption zip at the same time.

Flash that system image using Install > Install Image > Browse to the .img file

Flash disable-force-encryption if you formatted /data (don't flash it if you didn't do that !)

Flash Magisk.zip

Reboot and profit !

Note that there might be some issues with the GSI you choose. Most GSI suffers issues regarding Wifi Tethering/Hotspot. Other than that, check for my thread for issues regarding GSIs.

Some GSI require installation of GAPPS (Google Apps). Download a GAPPS zip and flash it at : https://opengapps.org/ (Choose ARM64 and 9.0)

If Installation fails, saying that system size is too small, go to (Wipe > Advanced Format > Tick "System" > Repair or change file system > Resize File System) and try flashing again.

INTERESTING MODS FOR ALL ROMS

Magisk FDE.AI

A great system manager. Saves a ton of battery without a performance hit. You need magisk installed. XDA Thread : https://xdaforums.com/apps/magisk/beta-feradroid-engine-v0-19-ultimate-t3284421

Fix SafetyNet not passing on custom ROMs/GSIs

SafetyNet will not pass by default on custom ROMs / GSIs.

Use Magisk Hide Prop Config : https://xdaforums.com/apps/magisk/module-magiskhide-props-config-t3789228

Run 'su' then 'props' in a terminal emulator. Edit Device fingerprint, choose Pick a certified fingerprint. I recommend using Xiaomi Redmi Note 7, as it changes the status-bar to be notch sized.

Note that you may need to do this next fix to make 'su' work :

Root request not working with Magisk

On some GSIs, root requests will not show up. You need to move some vendor files over to system.

Use TWRP's File Manager (Advanced > File Manager) or Adb shell to copy theses files :

/vendor/lib/libdirect-coredump.so

COPIED TO

/system/lib/libdirect-coredump.so

/vendor/lib64/libdirect-coredump.so

COPIED TO

/system/lib64/libdirect-coredump.so

This will fix this issue until GSI / ROM creator fixes it in their ROM;

Enjoy your new phone ! Don't forget to say thanks to all the developers behind every project (not me ! I didn't do anything :) )

If you have any issues, feel free to ask questions !

See you on the other side