[Asus ZenFone 4 Max Guides, News, & Discussion] Deleted member 12324997:
In this guide, i'm going to be a bit straightforward on how to install LOS 18.1 on your X00H/X00I device.

For the process, you need:

Your X00H/X00I device;

The following must be unlocked (if you didn't, you can follow the howto over my post);

A rooted phone/tablet with Magisk (any ADB & Fastboot tool is fine, but i suggest using this for simplicity);

In case you have none of the above, even a PC or Laptop with ADB and Fastboot binaries installed will suffice;

If you're on Windows, you can get the installer over GitHub;

If you're on Linux, hop into your package manager and install them via terminal (the following example will be for Debian/Deb-based/Ubuntu/Ubuntu-based distros. If you're on Arch, Fedora, etc.: just search for "fastboot" by using the respective pkg manager's search flag, then install it basing from the name it's repo gives):

sudo apt install fastboot

An USB cable (should come into the device's box, also must be capable of data transfering);

If you're going to do the process via a rooted device, the Asus device should come in it's packaging with an OTG adapter (be sure to attach the following to the rooted device);

PBRP (Pitch Black Recovery Project) for the device- OG post can be checked here;

Latest version for X00H;

Latest version for X00I;

If your device is an X00I, you can alternatively get TWRP instead;

The Android 9 Beta update (you MUST have the device updated to that version, else you'll risk the device to be bricked- for more info, check the OG post by Seba);

If you want to flash it via stock recovery, you can get the file over ASUS' site on the device;

Download for the X00H;

Download for the X00I;

If you have already flashed a custom recovery on your device, you can get the "custom recovery flashable zip"over SebaUbuntu's site;

.zip file for the X00H;

.zip file for the X00I;

Tiny discalimer on the flashable .zip above: once installed, your device's recovery will be replaced to stock (in other words, you'll lose the custom recovery);

The Lineage OS 18.1 rom and recovery (credits to @miya0405 for finding the site);

ROM and LOS Recovery for the X00H;

ROM and LOS Recovery for the X00I;

If you have all of the things required in the list, let's go!

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Installing the Android 9 Beta​

Stock Recovery method:​

Download the Android 9 Beta over ASUS' site (any device is fine, even using the phone itself);

Put an SDCard inside the device;

Move the .zip file inside the SDCard;

Turn off the device;

Boot into recovery (do Power + Vol.up combo- if your device's unlocked, tap on the volume button and select "Recovery" by pressing on the power button to confirm);

Select "Update from sd card";

Select the .zip file you've downloaded;

Wait for the update to install;

After updated, go back and select "Power off";

Custom Recovery Method:​

Download the Android 9 Beta flashable .zip over SebaUbuntu's site;

Put an SDCard inside the device;

Move the .zip file inside the SDCard;

Turn off the device;

Boot into recovery;

Select "Install";

Select the "External Memory" storage;

Search for the .zip file inside the SDCard;

Tap on it and install it, unchecking everything;

Swipe to continue and let the .zip file install;

The recovery will print you text on the progress (also gives advice on what to do after install);

Reboot to system;

Power off the device;

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Unlocking the device:​

Just a tiny reminder if you haven't yet, check my guide about it: then, resume from this point and proceed;

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!!A word of advice!!​

Don't install PBRP recovery just yet!

If you'll pick PBRP instead of the LOS recovery as the custom recovery of choice, flashing LOS 18.4 with it should make Lineage 100% unbootable and stuck in a bootloop!

Don't reboot back to PBRP if bootloops happen:

neither don't fix the "Cache" partiton with it, else it'll cripple more Lineage and redirect the boot to recovery or fastboot/bootloader!

TL;DR: Don't do my same mistake and flash the recovery partition with the wrong recovery (on the bright side, the device will still be salvageable).

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Flashing Lineage Recovery:​

Before proceeding, do the following firsthand:

Be sure to have the ADB & Fastboot binaries installed;

Your device rebooted to fastboot/bootloader mode (any method is acceptable);

Must have downloaded the recovery for your specific model (links are on the "required" list);

The device must be connected to the host machine (if you're using a rooted phone, be sure to have the OTG adapter connected to it first);

Rooted Android Device Method:​

Open the "ADB & Fastboot"tools of your choice;

Whether it is a terminal or the app i've suggested earlier: this portion will purely give instructions if you have the app;

If you're going to do the process via terminal, then jump to the "Linux Method" instead;

If it is the first time you open the tool, it should ask for root perms.- allow them;

Tap on the top right corner of the UI;

Tap on "Fastboot";

Tap on "Refresh";

Go to the "Partition" title, next to it you should see a dropdown menu;

Select "recovery";

Tap on the "Flash" button;

A file manager should open: search where the lineage recovery is (typically you can find it in the "Download" folder. The file should be called "recovery.img");

After selected, the app will automatically flash the recovery for you;

Disconnect the device;

Navigate over your Asus device with the volume buttons;

Select "Reboot recovery" and confirm with the power button;

Hooray, you have LOS Recovery installed;

Linux Method:​

Open the terminal (use the shortcut CTRL+ALT+T to open it, preferrably);

Do the following:

lsusb
# This checks if your asus device is connected proper to the machine
# If it is, lsusb should output something around a "Google" or "Qualcomm" device on the ID Bus
cd Downloads
# If you have put a different language locale, cd into the Downloads folder with it's localized name
ls
# List for the files inside the folder. You should see a file called 'recovery.img' inside
fastboot devices
# Tell fastboot to check if any device on bootloader/fastboot mode is connected
fastboot flash recovery recovery.img
# Gives fastboot the instruction to flash the .img file to the desired device's partition, which is the recovery in this case

After done flashing, disconnect the device;

Navigate over your Asus device with the volume buttons;

Select "Reboot recovery" and confirm with the power button;

Hooray, you have LOS Recovery installed;

Windows Method:​

GUI Method:​

Simply use the "Latest ADB Launcher"executable located on the desktop of your PC;

Just make sure to flash the recovery partition with the "recovery.img" file;

Terminal Method:​

Navigate with the File Explorer;

Go to your Downloads folder and find for a file called "recovery.img";

Cut and paste it to where the ADB and Fastboot tools are installed at;

Click on your mouse's right button;

Select "Open terminal here" over the contextual menu;

A terminal should pop-up (Command Prompt, that is);

Type in the following:

fastboot devices
fastboot flash recovery recovery.img

Wait for the recovery to flash on the device;

After done so, disconnect the device;

Navigate over your Asus device with the volume buttons;

Select "Reboot recovery" and confirm with the power button;

Hooray, you have LOS Recovery installed;

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Installing Lineage OS 18.1:​

Before proceeding, do the following firsthand:

Your device must be turned off;

Must have deleted the Android 9 Beta .zip file from the SDCard, for avoiding accidents;

Download the Lineage file off of the "required" list's links for your specific model;

Put the downloaded .zip file on an SDCard;

Insert the SDCard inside the device's slot;

Boot up into recovery mode;

Select with the volume keys "Apply Update" > "Apply from sdcard" and confirm with the power button;

Select the LineageOS .zip file;

Confirm with the power button;

Let the rom install by the recovery;

After install, navigate to the back button with the volume keys;

Select "Factory reset" > "Format cache partition";

The recovery will ask you the following:

Format Cache?
THIS CAN'T BE UNDONE!

Select "Yes";

Go back;

Select "Reboot system now";

First bootup will take some while, but you'll be greeted by the setup screen in no time.

Congratz, now your device has Lineage OS installed!

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Extras/FAQ Section:​

Q: Is it possible to get root priviledges on the device?​

A: Sure! There are different ways to apply root on the ROM, but feel free to pick whichever method you like:​

Rooting your device by picking it's 'boot.img' (exactly located on the folder of the respective model) over SebaUbuntu's Lineage site and patch it with an already-rooted device that has the Magisk companion app installed (requires no recovery patching, but it is required to boot the asus device in fastboot mode and patch the boot partition);​

Downloading the Magisk companion app over it's GitHub page, rename the .apk file by replacing '.apk' to '.zip' via file manager, patch PBRP over the recovery partition (with one of the methods listed over 2 titles above this one), and install the 'magisk.zip' file like you could usually do on any other device with custom recovery;​

If you use an X00I device, you can preferrably install TWRP from here instead of PBRP;​

After applied root on the device, patch back on the device the Lineage recovery- just for avoiding any inconvenience if you want to factory reset the device;​

Q: My device has Lineage installed, but the bottom buttons don't work. Is there a way to enable a virtual navbar?​

A: Yep, but it's a bit of a tricky process. You must have either apps like Terminal Emulator or Termux installed for making this work- as an extra, you could get other keyboards like BeHe Keyboard or Hacker's Keyboard: but that is only if you've picked Terminal Emulator as your choice.​

For direct instructions, follow this (you must be inside the terminal app of your choice and already gave storage perms to it firsthand):​

su
mount -o rw,remount /
vi /system/build.prop
# After come this far, go to the bottom of the build.prop file by scrolling with the touch screen
# On your keyboard, press the I key. This should make vi enter into INSERT mode
# When done so, add the following line on the build.prop file
qemu.hw.mainkeys=0
# For getting out of INSERT mode, find on your keyboard or terminal UI the ESC button
# For quitting and saving the file on vi, type the following
:wq!
# This should make vi quit and save the modifications to the build.prop file
# For rebooting the device straight from the terminal, just type in
reboot
# The device should immediately reboot, and upon unlocking: the virtual navbar should appear

Q: Can it be possible installing MicroG on the device?​

A: You can! Every method for installing MicroG perfectly works on this ROM;​

Q: I have MicroG installed on my device, but i want to apply signature spoofing for extra functionality. Is this possible?​

A: Sadly, due to the tinkering i've done on my side: the ROM gets a meltdown when modifying the 'services.jar' file is involved (root or non-root). If you follow some guides online (despite being few), the ROM,

regardless of what you do

or

which method you follow

: ​

it will end up in a bootloop (or, to be more specific, the SystemUI starts to become picky);​

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Credits:

miya0405 (for the lineage site)

SebaUbuntu (for the LOS rom, recovery, and PBRP recovery)

Erwin Abs (PBRP Recovery)

aaaaaaziskurnia (TWRP recovery for the X00I)

You, for dedicating your time on reading this long guide!