Refs:
1. http://os.archlinuxarm.org/os/ArchLinuxARM-aarch64-latest.tar.gz
2. https://dl-cdn.alpinelinux.org/alpine/v3.13/releases/aarch64/alpine-virt-3.13.5-aarch64.iso
3. https://wiki.alpinelinux.org/wiki/Replacing_non-Alpine_Linux_with_Alpine_remotely
4. https://wiki.archlinux.org/index.php/installation_guide#Configure_the_system
5. https://archlinuxarm.org/platforms/armv8/generic

Requirement:
  Console access.
  
1. In Oracle Linux 8.0
  cd /tmp
  wget https://dl-cdn.alpinelinux.org/alpine/v3.13/releases/aarch64/alpine-virt-3.13.5-aarch64.iso
  dd if=alpine-virt-3.13.5-aarch64.iso of=/dev/sda
  sync
  reboot
2. In Alpine w/ Console access:
# [Bring up networking]
vi /etc/network/interfaces, add:
  auto eth0
  iface eth0 inet dhcp
ifup eth0
# [Per Ref #3]
mkdir /media/setup
cp -a /media/sda/* /media/setup
mkdir /lib/setup
cp -a /.modloop/* /lib/setup
/etc/init.d/modloop stop
umount /dev/sda
mv /media/setup/* /media/sda/
mv /lib/setup/* /.modloop/
# [Setup apk and bring in pacman]
setup-apkrepos
vi /etc/apk/repositories, enable community
apk update
apk add dosfstools e2fsprogs libarchive-tools pacman arch-install-scripts
# [Disk partitioning & mounting]
fdisk /dev/sda(use gpt table, set esp partition 15 size 512M), set root partition 1 size remaining)
mkfs.vfat /dev/sda15
mkfs.ext4 /dev/sda1
mount /dev/sda1 /mnt
mkdir -p /mnt/boot/efi
mount /dev/sda15 /mnt/boot/efi
cd /mnt
wget http://os.archlinuxarm.org/os/ArchLinuxARM-aarch64-latest.tar.gz
bsdtar -xpf /mnt/ArchLinuxARM-aarch64-latest.tar.gz -C /mnt
genfstab -U /mnt >> /mnt/etc/fstab
arch-chroot /mnt/
pacman-key --init
pacman-key --populate archlinuxarm
# [EFI boot]
pacman -Syu grub efibootmgr
grub-install --efi-directory=/boot/efi --bootloader-id=GRUB
# [grub config]
grub-mkconfig -o /boot/grub/grub.cfg
# [workaround: grub of alarm doesn't detect linux]
echo "linux (hd0,gpt1)/boot/Image.gz root=/dev/sda1" >> /boot/grub/grub.cfg
echo "initrd (hd0,gpt1)/boot/initramfs-linux.img"    >> /boot/grub/grub.cfg
echo boot                                            >> /boot/grub/grub.cfg

vi /etc/ssh/sshd_config and update to "PasswordAuthentication no"
change to user 'alarm', create ~/.ssh and ~/.ssh/authorized_keys

At this point you should be able to issue 'reboot' and use ssh keyless login to remote into new alarm system.