It's obviously a pain to have to do this manually for every Ubuntu installation, but at least it makes nautilus more user-friendly again.
The upstream bug is flagged as resolved due to being a duplicate of what is actually not a duplicate bug, so I doubt upstream will take any further action.
Some information from the upstream bug: it turns out that it is configurable - the way to restore the backspace key functionality is to add:
(gtk_accel_path "<Actions> /ShellActions/ Up" "BackSpace")
to ~/.config/ nautilus/ accels.
It's obviously a pain to have to do this manually for every Ubuntu installation, but at least it makes nautilus more user-friendly again.
The upstream bug is flagged as resolved due to being a duplicate of what is actually not a duplicate bug, so I doubt upstream will take any further action.