Enable temporarily
I do not recommend enabling this permanently. You should probably add individual writable directories
         sudo apt update
        
         sudo apt install (package)
        
         sudo nano /lib/systemd/system/(service name, arbitrary).mount
        
        [Unit]
Before=local-fs.target
[Mount]
Where=(target location)
What=/userdata/system-data/(target location)
Type=none
Options=bind
[Install]
WantedBy=local-fs.target
       
         sudo systemctl enable (service name)
        
         sudo systemctl start (service name)
        Note: many Ubuntu Touch ports do not have DRM support, so a lot of DEs will not work
         sudo systemctl stop lightdm
        
         sudo systemctl disable lightdm
        
         sudo nano /lib/systemd/system/desktop.service
        
        [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
       
         sudo systemctl enable desktop
        
         sudo systemctl start desktop
        
         /etc/X11/Xwrapper.config
        
         allowed_users=console
         to 
         allowed_users=anybody
        
         sudo rm /lib/systemd/system/lightdm.service
        To update the screen once run: 
        cat /sys/class/graphics/fb0/modes > /sys/class/graphics/fb0/mode
        (as root)
         sudo nano /lib/systemd/system/fb-refresher.service
        
        [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
       
         sudo systemctl enable fb-refresher
        
         sudo systemctl start fb-refresher
        Enable temporarily
         sudo dd if=/dev/zero of=/userdata/swapfile bs=1024 count=(desired size in kilobytes) status=progress
        
         sudo chmod 600 /userdata/swapfile
        
         sudo mkswap /userdata/swapfile
        
         sudo swapon /userdata/swapfile
        Enable permanently:
         sudo nano /lib/systemd/system/swap.service
        
        [Unit]
Description=Enable swap
[Service]
Type=oneshot
ExecStart=/usr/sbin/swapon /userdata/swapfile
RemainAfterExit=yes
[Install]
WantedBy=multi-user.target
       
         sudo systemctl enable swap
        
         sudo systemctl start swap
        Installing nix:
         sudo chown -R phablet /nix
        
         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 preloaded
        . It can be safely ignored. To disable this warning:
         unset LD_PRELOAD
         to the end of 
         ~/.bashrc
        Installing home-manager: