As suggested on IRC, downgrading ncurses-term=6.0+20161126-1+deb9u2 and ncurses-base=6.0+20161126-1+deb9u2
makes the keys work in neovim again.
As suggested on IRC, downgrading ncurses-term=6.0+20161126-1+deb9u2 and ncurses-base=6.0+20161126-1+deb9u2
makes the keys work in neovim again.