Well, it seems that this problem may be solved with de compose key. As a matter of fact, it isn't activated by default, what is a very annoying problem. Moreover it's quite easy to use.
-- Can't type Spanish acutes with French keyboard layout on kde https://launchpad.net/bugs/76001 -- kubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/kubuntu-bugs
