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Windows 10 LTSC – the version that won't expire for years
(go.theregister.com)
This is a most excellent place for technology news and articles.
The issue I'm talking about is unrelated to keyboard layouts. It's how deadkeys are implemented.
The deadkeys are seemingly defined separately from keyboard layout, and there is no way that I could find to redefine them other than either turning dead key behaviour on or off in the keyboard layouts