OSDev.org

Currently I don't have an time to programming KISS'EM. I decided to switch direction. What about os, which support disabled persons from boot manager? I decided to create Linux distribution and enhance grub to support playing some wav. grub2-mkconfig will read menu entries (titles) and generate this wav. Additional, there will be some generic wav, containing "Press esc to ask me to read menu options". When computer launches, grub2 will tell "Press esc to ask me to read menu options". User press esc and grub say (for example):
Press 1 for OUR DISTRO. Press 2 for Windows bootloader, etc. As far as I known Linux kernel will have console spech synthesizer software. We could omit these special features, when user doesn't click esc on livecd version (before install OS), but we enable spech generator bot for live cd and installed systems, when user press esc on livecd's grub2 menu.

Unfortunately, this way you fall into the deep hole known as "sound support". While it is possible, trivial even, to make screen outputs before the OS is loaded, accessing PCM playback capability requires a lot of work. You'd need to crawl PCI, find the sound card, have a driver ready for it. That is not really straightforward, and you'd have to do most of the work. More attainable might be using the PC speaker to give a different number of beeps, or different pitches, depending on the option. That way, a blind person would only have to know the options from being told them once. Actually, grub-mkconfig could read those options out to the user, but that presumes that the user will be present when the update happens. Also, this runs afoul of the problem that most PCs sold these days no longer have a PC speaker. And many don't even emulate it. So yeah, sound is probably unattainable at the boot loader stage.

There exist another (possible) way to achieve a goal. There exist rumors Linux developers discuss about implementing in-kernel boot loader. Even, very long ago, Canonical creator have idea to implement user-space boot loader. These boot loaders will interact, when OS is loading, not before, not after. So maybe we will have possibility to access indirectly the sound card. But, unfortunately I don't known much about UEFI and KMS.

How I will try to solve this? I will write a small KMS app, which will be started before Plymouth. It will asks which OS to ran. If user decided to ran current one, we will ran (spawn) Plymouth and exit. On other cases, we will tell grub2 which OS to ran and restart, so maybe it will worked even without UEFI support. Grub2 will ran our/my OS by default.

That would probably work. Windows 8 and 10 did this. I remember getting annoyed by having to reboot twice when I wanted to use Win7 or XP