"space enter F5 3 enter down enter" is not a discoverable key sequence for the screen reader install
Binary package hint: casper
to do an install with the help of the orca screen reader you have to press space after the bios, then enter to select English language then F5 for the accessibilty options menu, then 3 for the screen reader, then enter to select it, then down to install ubuntu (hard to get to the installer from the "try" option) then enter to start the install. Some time later it starts talking to you. This is not an easy sequence of events to follow without vision. It would be great to have a shortcut to press that just starts the installer.