It is still there on my Linux OS but hasn't worked for some years. I have had to use KDE to hide the title bar; perhaps you can do something similar. Check about:policies in case your distro is disabling the option.
I think the option might just be disabled, yeah. On lubuntu I was able to right click the title bar and disable decoration. Can't do that on xfce tho and that's the wm my main machine uses. Guess I'll try updating and deal with the consequences later?