Some users may need specific support because of e.g. some visual impairment. Most accessibility features have to be enabled manually. Some boot parameters can be appended to enable accessibility features. Note that on most architectures the boot loader interprets your keyboard as a QWERTY keyboard.
The Debian installer supports several front-ends for asking questions, with
varying convenience for accessibility: notably,
uses plain text while
newt uses text-based dialog
boxes. The choice can be made at the boot prompt, see the documentation for
DEBIAN_FRONTEND in Section 5.3.2, “Debian Installer Parameters”.
Some accessibility devices are actual boards that are plugged inside the
machine and that read text directly from the video memory. To get them
to work framebuffer support must be disabled by using the
boot parameter. This will however reduce the number of available languages.
For users with low vision, the installer can use a high-contrast
color theme that makes it more readable. To enable it, append the
theme=dark boot parameter.
Alternatively, Debian can be installed completely automatically by using preseeding. This is documented in Appendix B, Automating the installation using preseeding.
Documentation on accessibility of the installed system is available on the Debian Accessibility wiki page.