We'll install it with Linux Deploy

This instruction is for OnePlus6(T), but can be reproduced on the other devices (btw you need special nethunter kernel)

Install DJY's Android 9 kernel (click to download - Magisk v20.1 included) OR kimocoder's Android 10 kernel (click to download)

Install Magisk module by DJY or modified one by me from Magisk Manager

Install BusyBox from Magisk repo or from GitHub

You're ready!

Download & install Linux Deploy

Download kalifs and place in at /sdcard/kalifs-armhf-full.tar.xz (/storage/emulated/0/kalifs-armhf-full.tar.xz)

Using any root file explorer, create folders at "/data/local/nhsystem/kali-armhf"

Open Linux Deploy and set settings as shown on the pictures (click)

Click on 3 dots in top right corner -> Install

Wait 5-7 minutes

Then click STOP, wait, START

Open Terminal -> Android SU

Click on 3 dots in top right corner -> Config Chroot Path and replace "arm64" with "armhf"

Restart Terminal -> Kali

Finally, write "apt update && apt upgrade -y && apt dist-upgrade -y" to update Nethunter

Now you can safely delete Linux Deploy

If you'll try to "apt update" - you may get an error

To fix that write "apt-key adv --keyserver hkp://keys.gnupg.net --recv-keys 7D8D0BF6", but if it doesn't works - replace "7D8D0BF6" with key that can't be verified (specified in "apt update" error)

If you need to start ssh - "service ssh start"

But you may can't connect to your phone

To fix that write "nano /etc/ssh/sshd_config" and find "PermitRootLogin yes" - uncomment it. Now find "UsePAM yes" and replace it with "UsePAM no"

Now "passwd" to change root password if needed & "service ssh restart"

Nethunter contains 2 versions of "iptables", so default doesn't works for me

Simply write "mkdir -p /root/scripts && mv /usr/sbin/iptables /root/scripts/ && ln -s /usr/sbin/iptables-legacy /usr/sbin/iptables"

P.S. Thanks to @SymbianSyMoh

For the people who were asking regarding the packages that breaks the terminals title window and other windows title bars, just avoid installing ANYTHING related to XFCE window manager, this need some careful as some related packages can be installed without your consent for example (when installing kali-linux-nethunter package), so the suggestion is to have a clean Linux Deploy installation with LXDE window manager and then to be careful with the anything packages related to XFCE-* window manager.

As the other issue of why sometimes the VNC is breaking, also avoid anything related to TigerVNC, just don’t install it or anything related and if installed, just remove it (apt-get purge tiger* -y)

Just write "source /etc/profile && source /root/.bash_profile"

Open Nethunter app -> USB Army -> USB Interface -> hid -> Set USB interface

or

Open Terminal -> Android SU and write:

setprop sys.usb.config win,hid
setprop sys.usb.config win,mass_storage
setprop sys.usb.config win,rndis
setprop sys.usb.config win,hid,mass_storage
setprop sys.usb.config win,rndis,hid
setprop sys.usb.config win,rndis,mass_storage
setprop sys.usb.config win,rndis,hid,mass_storage
setprop sys.usb.config mac,hid
setprop sys.usb.config mac,mass_storage
setprop sys.usb.config mac,ecm
setprop sys.usb.config mac,hid,mass_storage
setprop sys.usb.config mac,ecm,hid
setprop sys.usb.config mac,ecm,mass_storage
setprop sys.usb.config mac,ecm,hid,mass_storage
setprop sys.usb.config win,hid,adb
setprop sys.usb.config win,mass_storage
setprop sys.usb.config win,rndis
setprop sys.usb.config win,hid,adb,mass_storage
setprop sys.usb.config win,rndis,hid,adb
setprop sys.usb.config win,rndis,mass_storage
setprop sys.usb.config win,rndis,hid,adb,mass_storage
setprop sys.usb.config mac,hid,adb
setprop sys.usb.config mac,mass_storage
setprop sys.usb.config mac,ecm
setprop sys.usb.config mac,hid,adb,mass_storage
setprop sys.usb.config mac,ecm,hid,adb
setprop sys.usb.config mac,ecm,mass_storage
setprop sys.usb.config mac,ecm,hid,adb,mass_storage

HID interface may not be displayed in Nethunter, but it does exists :)

Do "apt install zsh -y"

Then we need to install Oh-my-zsh - "git clone https://github.com/robbyrussell/oh-my-zsh.git && cd oh-my-zsh && ./oh-my-zsh.sh"

Install it as default shell

I've installed this dot files, so they're working almost perfect.

"git clone https://github.com/dikiaap/dotfiles", then "cd dotfiles && ./install.sh && zsh"

You can add your functions in "~/.functions", for example:

# Update
apt-update() {
    sudo apt update
    sudo apt upgrade -y
    sudo apt dist-upgrade -y
    apt-clean
}

If there'll be any problems:

Run "wget https://raw.githubusercontent.com/rupa/z/master/z.sh && mkdir ~/.zsh/plugins/z && mv z.sh ~/.zsh/plugins/z/z.sh"

Just create these files ("touch ~/.functions_private && touch ~/.aliases_private") or remove their references in ~/.zshrc

Run "touch ~/.numpad", add in end of "~/.zshrc" "source ~/.numpad" add in this file these lines:

# Keypad
# 0 . Enter
bindkey -s "^[Op" "0"
bindkey -s "^[Ol" "."
bindkey -s "^[OM" "^M"
# 1 2 3
bindkey -s "^[Oq" "1"
bindkey -s "^[Or" "2"
bindkey -s "^[Os" "3"
# 4 5 6
bindkey -s "^[Ot" "4"
bindkey -s "^[Ou" "5"
bindkey -s "^[Ov" "6"
# 7 8 9
bindkey -s "^[Ow" "7"
bindkey -s "^[Ox" "8"
bindkey -s "^[Oy" "9"
# + -  * /
bindkey -s "^[Ok" "+"
bindkey -s "^[Om" "-"
bindkey -s "^[Oj" "*"
bindkey -s "^[Oo" "/"

Source