Continuing the discussion from Spell check doesn’t work:
It is disconcerting that spell check (as you type) doesn’t work unless you use English (USA) in all language settings. (<Options…> [check out 3 entry points])
The same situation occurs in Open Office.
The US lanuage invariably will drop “u” from words like “colour”. These “quirks” can be added to your custom dictionary, The spell check wil pick these up in the future.
It is a program error (and possibly very early in the development of the suites). It applies to Calc as well as Write.
The program should “remember” your new settings.
Could you give more technical details? At least OS name, LO version and save format.
I write documents in several languages and, among these, I prefer English (UK) over English (USA) and have no problem.
When I create multi-lingual documents, spelling is correctly checked in the “local context”. Perhaps, attach a “faulty” 1- or 2-page document so that we can have a look at it.