Is it possible to also add some logic to populate boot entries using https://uapi-group.org/specifications/specs/boot_loader_specification/ ? I have been experimenting with systemd-boot, and it's working fine apart from the missing loader files. Those files look something like this:
/usr/lib/live/mount/persistence/loader/entries/1.4-rolling-202210050218-vty.conf
title "VyOS 1.4-rolling-202210050218 (KVM console)" version 1.4-rolling-202210050218 options boot=live quiet rootdelay=5 noautologin net.ifnames=0 biosdevname=0 vyos-union=/boot/1.4-rolling-202210050218 console=tty0 linux boot/1.4-rolling-202210050218/vmlinuz initrd boot/1.4-rolling-202210050218/initrd.img
There will be similar files for serial and USB console.