Like Tex I don't like faking the language code which is one reason I tried to come up with an empty dictionary approach. However as you can use any legal language code I think I'm going to use the one for Ido (io) - a little used variant of Esperanto and for which it is unlikely there is a dictionary ! (or much literature in the language)
Libre Office gets round this by having a setting under "Language" of "None" (Ignore spelling) but doesn't have a setting for Ido
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BobC