<Fn><F2> and <Fn><Fn><F3> without effect

[farinet at arcor.de]

John Hupp:
> The file to edit is ~/.config/openbox/lubuntu-rc.xml.  That covers
> per-user settings.  I don't know of a way to solve it globally for all
> users.
> 
> The most comprehensive single resource I know about for dealing with
> special keys is https://help.ubuntu.com/community/MultimediaKeys

Thanks for the pointer. The article on help.ubuntu, for me and for sure
it's my fault (too less knowledge), it's a mess. It's really
complicated. I tried to follow, but already at the first two steps it
did not work: Pressing the <Fn>keys in the console results in nothing,
but the keys are there, as i'm told by xev. <Fn><F3> and <Fn><F2> even
open the popup window with the brightness bar - but
increasing/decreasing results in no effect.

For <Fn><F6> thru <Fn><F8> (volume control) nothing happens at all. But
that might be due to the misteries of pulse audio (?)