Comment 31 for bug 1050855

d-i doesn't do anything special with keyboards, as far as I know; it just relies on the kernel and udev to bring stuff up and then lets the normal console input layer do its work.

It's possible that something is missing from udev-udeb, I suppose. However, I just had a look through there and couldn't see anything obvious.

All the next steps I can think of are fairly non-trivial. One possibility would be to remaster the image to get rid of the "quiet" parameter in isolinux/isolinux.cfg (though this is relatively easy if you're booting from CD - just edit that file directly) and then video the startup process to capture kernel messages scrolling by.