Try initializting keyring on archiso side

http/install.sh

@@ -26,7 +26,8 @@ mkfs.btrfs -L "rootfs" "${device}2"
 mount -o compress-force=zstd "${device}2" /mnt
 
 echo "Server = ${MIRROR}" >/etc/pacman.d/mirrorlist
-pacstrap -M /mnt base linux grub openssh sudo polkit haveged netctl python
-echo "Server = ${MIRROR}" >/mnt/etc/pacman.d/mirrorlist
+pacman-key --init
+pacman-key --populate archlinux
+pacstrap /mnt base linux grub openssh sudo polkit haveged netctl python
 
 arch-chroot /mnt /bin/bash