Using the keycode instead of the keysym should work. You can also find it in the xev output. For me it's:
xmodmap -e "keycode 108 = Alt_R Meta_R Alt_R Meta_R"
How to replace Alt gr with Alt R?
Using the keycode instead of the keysym should work. You can also find it in the xev output. For me it's:
xmodmap -e "keycode 108 = Alt_R Meta_R Alt_R Meta_R"