Just wanted to share some findings after trying to multiboot Windows, Solus, and Ubuntu. I was trying to figure out a good way to organize booting from each (because my hp-envy has frustrating non-standard handling of boot entries) and came across some Clr-boot-manager/systemd-boot documentation from Clear Linux. Yes, I realize there is history/heritage, but nonetheless, in case this helps anyone else with their efforts to interface with a Grub-based distro:
https://docs.01.org/clearlinux/latest/tutorials/multi-boot/dual-boot-linux.html
As an update, since I currently don't seem to have anything under /boot/efi/com.solus-project (supposedly would be a file bootloaderx64.efi), I pointed my grub entry at /efi/systemd/systemd-bootx64.efi and have mulitboot via grub working for now. If I end up with a different systemd booting distro, this may change, haha, but for now it works.
