Under Lubuntu 16.04 with mlterm 3.5.0, the option --borderless=true produces no effect, decorations stay, both if launched from command line, or in the main file.
I tested mlterm-3.5.0 on gnome-shell(3.24.2-1) and openbox(3.6.1-3)/LXDE on ArchLinux, but I haven't reproduced this problem yet.
Which window manager do you use ?
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I haven't reproduced it yet, but openbox seems to ignore MWM_HINTS_DECORATIONS property which mlterm sets on your system. For now I don't know why.
If you use "urxvt -bl" and the same problem happens, it might be caused by your configuration of openbox.
I'm not familiar with openbox, but I think adding following lines to your ~/.config/openbox/rc.xml or ~/.config/openbox/lxde-rc.xml is another way to solve it. How about it?
I tested mlterm-3.5.0 on gnome-shell(3.24.2-1) and openbox(3.6.1-3)/LXDE on ArchLinux, but I haven't reproduced this problem yet.
Which window manager do you use ?
I haven't reproduced it yet, but openbox seems to ignore MWM_HINTS_DECORATIONS property which mlterm sets on your system. For now I don't know why.
If you use "urxvt -bl" and the same problem happens, it might be caused by your configuration of openbox.
I'm not familiar with openbox, but I think adding following lines to your ~/.config/openbox/rc.xml or ~/.config/openbox/lxde-rc.xml is another way to solve it. How about it?
<applications>
...
<application name="mlterm">
<decor>no</decor>
</application>
...
</applications>
I'm sorry but I haven't test Lubuntu 16.04 yet.
Regards,