@peterx14 I did a few more experiments. One needs a new gnome session altogether for the 'headerbar' false change to work. I tried this a few times to confirm. Just killing all the terminals is not enough. However, when I login/out or kill gnome-session to restart the session manager, the problem is fixed. The side effect is that one loses all the nice gnome-terminal decoration (hamburger menu, find button, etc.). Oh well. Take your choice.
@peterx14 I did a few more experiments. One needs a new gnome session altogether for the 'headerbar' false change to work. I tried this a few times to confirm. Just killing all the terminals is not enough. However, when I login/out or kill gnome-session to restart the session manager, the problem is fixed. The side effect is that one loses all the nice gnome-terminal decoration (hamburger menu, find button, etc.). Oh well. Take your choice.