RH8, would it be possible to add additional language support after installation?
 

thx.

Yes. Install locales packages for the new language. I mean: locales-??, kde-i18n-?? etc.

What about the menu language change that Kde and Gnome support.

Is it different from language support?

I am talking about the menu language change that we can bring about by selecting language from the login menu.

You can choose language from it only when there are language packages installed. It's what you do when the packages are in your system.