Here’s my idea for adding the “Archlinux” entries.
However, I don’t know how to add the punctuation; currently, I know it’s not correct.
# Bootloader.
boot.loader.systemd-boot.enable = true;
boot.loader.efi.canTouchEfiVariables = false;
boot.loader.systemd-boot.extraEntries
{ "arch.conf" = ''
tittle Arch Linux (linux)
linux /vmlinuz-linux
initrd /initramfs-linux.img
options root=/dev/rootvg/rootlv rw
"; }
{ "arch-fallback.conf" = "
title Arch Linux (fallback initramfs)
linux /vmlinuz-linux
initrd /initramfs-linux-fallback.img
options root=/dev/rootvg/rootlv rw
"; }