AMD64 kindly writte instructions how to implement the famous Gentoo architecture to laptop system are out of scope for an ordinary developer, not even surpassing the threshold to intervene into the unknown.
The point made there is about SystemD (optional) article to embed, for example, Gnome desktop environment – is missing key components such as down to earth Grub 2 instructions, making the developer look like amateur MIG developer, keen on rendering assembler code intros to the MBR GRUB level.
What makes more sense is that PC level architecture binding of key combos like DEL, F1, F12 and so on are ubiquitous, printed on screen if not turned off and literally asking to press them daily. Then logged in firmware settings (so called previously up to now – recently – BIOS) show off UEFI preinstalled Windows 8.1, shipped securely & booted. What’s next – clear: setup mode UEFI boot and Gentoo distro secure keys storing to complete custom UEFI boot stage, rendering secure boot on.
Unluckily, this isn’t the case – booting is the hardest part for Gentoo, putting aside OpenRC generic sections takeover, SystemD retaining the unlearned lessons phase.