I know this question is off-topic but I have searched google for days writtin to numerous forums but nobody seems to be able to know a solution.
I use Ubuntu with the latest FVWM. I use a danish keyboard .
The thing is that I cannot type chars that depends on Alt-Gr (AT, Pipe, tilde etc) . I have been told to edit my .XF86Config-4 file to this:
Section “InputDevice”
Identifier “Generic Keyboard”
Driver “keyboard”
Option “CoreKeyboard”
Option “XkbRules” “xfree86”
Option “XkbModel” “pc105”
Option “XkbLayout” “dk”
Option “XkbVariant” “dk”
EndSection
But still I cannot type the above described chars. Actually I cannot type them in the login screen before I enter FVWM.
The wierd thing is that if I chose to start KDE instead it works fine.
Hope someone (eventhough this is off-topic) will help because I have spend a lot of days on this problem without finding any solution.
I don’t know a thing about Ubuntu, but I’m going to try to help anyway.
Try to see if you can find something obvious from /var/log/XFree86.0.log
(ie if "Using config file: “/path/to/somewhere/XF86Config” is some other file than what you have edited, ie if ubuntu is using xorg, the config file is likely not called XF86Config, nor the log-file)
Have you tried running ‘xf86config’ or some other (xorg’s?) similar graphical X-setup program?
You could try to find better match from there than just “generic PC 105-key” keyboard.
What is the graphical login manager (if any)? ie gdm, kdm, xdm etc.
It could be that some environmental variables need to be set up.
It could be that if X is running in virtual console, that’s settings need to be localized or something.
I struggled with same thing but in some bsd about a year ago, but I don’t remember how I corrected it 
Also could try:
~/.inputrc:
set meta-flag on
set convert-meta off
set output-meta on
That’s all I can think of at the moment.
if you use xorg, try to omit the line Option "XkbRules" "xfree86" and see if that helps.
test what xev reports upon ALTGR press.
this should give you some hints where to go.