I've got a laptop configured to dual-boot Windows 10 and Gentoo that I want to add an Ubuntu installation to so that I can do firmware updates (the OEM currently only supports handling of firmware updates on Ubuntu and Ubuntu derivatives).
In this particular case, I'm not directly using the UEFI boot manager other than having it load GRUB2 both because the system in question doesn't provide the option of a menu with a timeout (you have to hit F12 to get a boot menu, and it sits there until you select something), and because I want passwords on some boot options but not others (and Windows is one of the things I want a boot password for). I would like to keep this setup and integrate Ubuntu into it, instead of having to deal with the (crappy) UEFI boot manager interface when I want to boot Ubuntu, which in turn means I need a way for Ubuntu to not mess with the UEFI boot manager variables (fighting with Windows every time it gets upgraded to a new build is bad enough without another OS contending for control).
Based on what I've seen so far it looks like the only way to do this is to do a non-EFI install of Ubuntu, and then pull in the grub-efi package manually (and probably do some trickery to keep efibootmgr from being run). Is there any other way to do this without needing to create a custom installer or custom grub-efi package?