Just a cosmetic fixup (until not paired up with translations):
"2nd" means "second", "1st" meant "first".

use/grub/localboot, use/grub/sdab similar to use/syslinux/localboot,
use/syslinux/sdab.

Note: syslinux --install needed /proc, so:
@$(call set,GLOBAL_HSH_PROC,1)

See-also: mkimage/doc/README.ru

memtest is not part of syslinux.
Also replace tabs to spacebar.

At the moment, the ability to select the kernel with which to boot is
implemented only for grub (grub-pc, grub-efi, ieee1275boot).
note that renamed STAGE1_KFLAVOUR to STAGE1_KFLAVOURS, as multiple
kernels can now be added.

This reverts commit 5848ae70.

For riscv64 available grub-efi.
Needed added support for mkimage (mki-copy-efiboot-chrooted).

Not needed for other architectures.
See-also: use/branding/full

More than one BOOTLOADER may be available for the same architecture.
Set IMAGE_PACKTYPE in boot/iso, there is no point in duplicating
in different features.
Closes ALT bug 39786.

Thanks underwit@
See-also: ALT bug 39632

Needed for use one grub.cfg config for all grub platforms.

It is required to set the BOOTLOADER and BOOT_TYPE variables in
grubpcboot.

In menu you need the name of the distributiv.
If not set, then we will be as before.
Also corrected the selection of phrases for translation.
Suggested-by: zerg@
See-also: ALT bug 39611, 39612.

Pay attention to what you are adding to the variable. No need to
add language and live_rw there! Они нужны только для refind.

Otherwise it might e.g. add branding-*-bootloader
for no good reason, poisoning $destdir with an
existing and non-empty /etc/sysconfig/grub2
regardless of the actual grub availability
on the platform.

Example:
@$(call set,GRUB_DEFAULT,uefi-firmware)
@$(call xport,GRUB_DEFAULT)

See features.in/grub/cfg.in/*.cfg

60 seconds should be enough for any hardware.
It is important not to forget that the timeout for grub is measured
in seconds, and for syslinux in deciseconds.

Simply Linux has a specific directory name with a theme.