Systemd-boot and Grub together?

Here’s a little off topic.

I didn’t know that the comment told about EFIFS (it’s called EFI filesystem drivers) from your link of reddit. I researched it a bit, this may support multiple different filesystems and is based on GRUB2 driver.

systemd-boot developer already planned to load any driver into EFI stub, that I suspect.
See: https://github.com/systemd/systemd/issues/15617

Archlinux will plan to support for systemd-boot reading filesystems with EFI driver or not: