Here's some useful tips I collected about Ubuntu Touch. I used for a little, but decided agains it because the version for my Redmi 9 didn't have working Libertine (the Linux app container), making it unable to run Linux apps in the default DE.

I also tried to set up a custom window manager, but the ofono system is pure pain. Would not recommend this OS to the kind of nerd who would install Linux on their phone (wait a minute...)

Official website

Making the root partition read-write

Enable temporarily

• Open "System Settings"
• In "About" enable "Developer Mode"
• Install "UT Tweak Tool" from OpenStore
• Open "UT Tweak Tool"
• In the menu (top-left) select "System"
• In "Make image writable" select "[Read-Write]"

I do not recommend enabling this permanently. You should probably add individual writable directories

SSH Access

• Open "System Settings"
• In "About" enable "Developer Mode"
• Install "UT Tweak Tool" from OpenStore
• Open "UT Tweak Tool"
• In the menu (top-left) select "System"
• In "SSH Settings" enable SSH access

Installing packages

• Make the root partition read-write
• Run sudo apt update
• Install using sudo apt install (package)

Create writable directories in root

• Make the root partition read-write
• Run sudo nano /lib/systemd/system/(service name, arbitrary).mount
• Enter the following:

[Unit]
Before=local-fs.target

[Mount]
Where=(target location)
What=/userdata/system-data/(target location)
Type=none
Options=bind

[Install]
WantedBy=local-fs.target

• Run sudo systemctl enable (service name)
• Run sudo systemctl start (service name)

Changing the desktop environment

Note: many Ubuntu Touch ports do not have DRM support, so a lot of DEs will not work

• Make the root partition read-write
• Run sudo systemctl stop lightdm
• Run sudo systemctl disable lightdm
• Run sudo nano /lib/systemd/system/desktop.service
• Enter the following:

[Unit]
Description=User Session Starter
Conflicts=getty@tty7.service plymouth-quit.service
After=systemd-user-sessions.service getty@tty7.service plymouth-quit.service

[Service]
ExecStart=/usr/bin/su phablet -c (session command e.g. startx)
Restart=always

[Install]
WantedBy=graphical.target

• Run sudo systemctl enable desktop
• Run sudo systemctl start desktop

Setting up startx

• Make the root partition read-write
• Install xinit
• Set up your .xinitrc
• Edit /etc/X11/Xwrapper.config
• Change allowed_users=console to allowed_users=anybody

The screen turns off after a minute

To fix permanently

• Make the root partition read-write
• Run sudo rm /lib/systemd/system/lightdm.service

The screen does not update when running an X11 WM

To update the screen once run: cat /sys/class/graphics/fb0/modes > /sys/class/graphics/fb0/mode (as root)

To fix permanently

• Make the root partition read-write
• Run sudo nano /lib/systemd/system/fb-refresher.service
• Enter the following:

[Unit]
Description=Fix the screen

[Service]
ExecStart=/usr/bin/sh -c "while [ ! ]; do cat /sys/class/graphics/fb0/modes > /sys/class/graphics/fb0/mode; done"

[Install]
WantedBy=multi-user.target

• Run sudo systemctl enable fb-refresher
• Run sudo systemctl start fb-refresher

Enable swap

Enable temporarily

• Run sudo dd if=/dev/zero of=/userdata/swapfile bs=1024 count=(desired size in kilobytes) status=progress
• Run sudo chmod 600 /userdata/swapfile
• Run sudo mkswap /userdata/swapfile
• Run sudo swapon /userdata/swapfile

Enable permanently:

• Make the root partition read-write
• Run sudo nano /lib/systemd/system/swap.service
• Enter the following:

[Unit]
Description=Enable swap

[Service]
Type=oneshot
ExecStart=/usr/sbin/swapon /userdata/swapfile
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

• Run sudo systemctl enable swap
• Run sudo systemctl start swap

Installing nix and home-manager

Installing nix:

• Create /nix
• Install curl
• Install xz-utils
• Disable writable root
• Run sudo chown -R phablet /nix
• Run sh <(curl -L https://nixos.org/nix/install) --no-daemon

You might get ERROR: ld.so: object 'libtls-padding.so' from LD_PRELOAD cannot be codeloaded. It can be safely ignored. To disable this warning:

• Add unset LD_PRELOAD to the end of ~/.bashrc

Installing home-manager:

• Follow the home-manager standalone guide