[NOTE] Install Ubuntu server on Raspberry Pi 4 using smartphone

50-cloud-init.yaml

# This file is generated from information provided by the datasource. Changes
# to it will not persist across an instance reboot. To disable cloud-init's
# network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
network:
    ethernets:
        eth0:
            dhcp4: true
            optional: true
    version: 2
    wifis:
        wlan0:
            dhcp4: true
            optional: true
            access-points:
                "<ssid>":
                    password: "<plain_text_password>"

install.sh

# 1. umount mmc card using Setting > Storage

# 2. extract .img from tar.xz downloaded from 
#     https://old-releases.ubuntu.com/releases/focal/ubuntu-20.04.1-preinstalled-server-arm64+raspi.img.xz

# 3. write image to sdcard
dd if=/sdcard/ubuntu-20.04.1-preinstalled-server-arm64+raspi.img of=/dev/block/mmcblk0

# 4. create dir to mount partition w/ RW etc folder
su
mkdir /mnt/rp

# 5. mount partition
mount /dev/block/mmcblk0p2 /mnt/rp

# 6. copy 50-cloud-init.yaml (example file included)
cp /sdcard/50-cloud-init.yaml /mnt/rp/etc/netplan/

# 7. unmount partition
umount /mnt/rp

# 8. enable ssh
mount /dev/block/mmcblk0p1 /mnt/rp && touch /mnt/rp/ssh && umount /mnt/rp

# 9. insert microSD card into Raspberry Pi and enjoy!