Can I boot a ZFS install from a USB with just the boot loader installed?

[trevmlt]

I have a ZFS Proxmox 7 installation using the systemd-boot bootloader on an old spinning disk I would like to upgrade to an NVMe drive. My currrent (older) motherboard will not boot from NVMe without a BIOS hack, which I would like to avoid if possible. Is there a way to boot from a USB stick, but run the system from the NVMe with my configuration? I found a couple of bits of info here and there, but nothing recent (most talk involves grub).

 

[trevmlt]

With UEFI/systemd boot this does work on an Asrock EP2C602-4L/D16. After moving the rpool around between the NVMe and spinning disk, it was just a matter of formatting and copying the 1st and 2nd partitions to the USB, and then making sure the sticks UUID was present in /etc/kernel/proxmox-boot-uuids. Rebooted and system came up.