Need Advice on switching from systemd to grub on a dual boot on multiple disks

[TLATER]

@RZeugma

Is it possible to have a grub selection screen that encompasses both ?

You can accomplish this with systemd-boot too, using extraEntries and windows.

I personally agree that using the system boot menu is generally better, though. That’s UEFI working as intended. Just find the shortcut that lets you pick a bootloader rather than the shortcut that opens BIOS and use that.