test: 115.43'C, 58'c, 100'F, 1000'K
test: 100kg, 60g, 100mg
test: 0x01 0x10 0x4321 0x1023
A cellphone was obtained, with the desire to run LineageOS, in order to maintain control over the hardware.
The solutions available on the internet ranged from fastboot methods that did not work well due to being obsoleted to scripts that did not work for this or that reason.
As a bonus, Android 9 can be used instead of stock Android 8.1.
This will erase all data from the phone. Backup all or work with a fresh unit.
When working with a donated unit, do not forget to remove the user account which is logged to the app store. Otherwise there is a risk of triggering the "FRP lock", where the phone insists on logging in to this account before continuing with setup. Removal of this without the account information tends to be annoying. In theory, this is a measure against phone thieves. In practice, it is a headache for hand-me-down uses, and different types of phones tend to require different methods - the merchants buying the stolen equipment of course have both the tools and the knowledge.
Tools used are fastboot and adb, both in linux and windows versions.
fastboot is for communication with the phone in the bootloader mode. Flashing, variable interrogation, and reboots to different modes are possible here.
The bootloader mode can be accessed with powering the phone on with simultaneously pressed volume-up key. Fairly standard android method. Another method is via adb, adb reboot bootloader.
Windows version of fastboot tended to get confused and refused to get variables from the phone. This initially caused some scare as it was thought the automatic script may have damaged the bootloader.
It is said this can be cured by rebooting windows, but it may also return back. Operations with linux version were more reliable, however that version was older and did not support some commands, namely the "flashing" one.
Individual variables queried were failling too.
Protocol is described at https://android.googlesource.com/platform/system/core/+/master/fastboot/.
adb is for communication with the phone after booting, or in sideload mode. File transfers, shell, reboots to different modes, and other operations are possible.
Linux version was a little old, the TWRP recovery sideload mode required a newer version.
Phones are different. The unlock script refers to variables not present on this specific model, and to their values.
The app was downloaded via Chrome but it refused to install. Maybe it would work from sideload, was not tested. This "official unlock" is said to void the warranty and to not be undoable.
Full "canned" solutions containing fastboot.exe, adb.exe and related DLL files, and a .scr or .bat script that does the multistep job, exist. They are however prone to fail in edge cases, when something goes wrong.
Two phone-specific variables are needed:
To convince the phone to allow the unlock operation, the secret key has to be flashed to the "random partition".
We prepare the file to flash
and flash the file
Now we are prepared. We unlock it further. (Here the issue with linux fastboot not supporting the "flashing" command was encountered. The phone was reconnected to the Windows machine.)
We check if it really works.
Earlier we obtained the TWRP binary image for the proper phone version; it is NECESSARY to match the version with the phone, or it is likely to not work!
Download from here: https://forum.xda-developers.com/asus-zenfone-max-pro-m1/development/recovery-unofficial-twrp-3-2-3-0-t3888110
Now follow the instructions from the page.
Flash the binary:
Congratulations, TWRP is installed.
Now, stabilize it:
(or power-on with volume-down pressed)
And when asked to swipe to allow modifications, swipe. This trips the Android Verified Boot and allows modifications. Otherwise the system could recover the recovery partition to its original form.
The adb sideload method did not work due to the old version of adb.
Alternative method was used, with files loaded to the microSD card.
The main file is lineage-16.0-2020xxxx-nightly-X00TD-signed.zip.
The supplementary file for root was downloaded from https://download.lineageos.org/extras, file addonsu-16.0-arm64-signed.zip was used.
Google apps package was downloaded from https://androidfilehost.com/?flid=170282&w=files, file MindTheGapps-9.0.0-arm64-20190615_031441.zip.
All three files were loaded to the microSD card, the card placed to the phone, the phone booted to recovery. Instructions with wiping partitions from the lineageos installation guide were followed, up to the point where adb sideload is used.
LineageOS was then attempted to be flashed. The operation failed, with error message about a version of firmware.
File PIE_20190401_firmware.zip was located by google and added to the sd card.
Files were flashed one by one, in sequence
After reboot, rooted LineageOS was running on the phone.
download Magisk from https://magisk.me/: