Some devices, most notably some braille keyboards/chorded keyboards, don't provide keycodes but keysyms (virtual keyboards too, but they're outside libinput's scope). The conversion from input to keysyms can be device-specific. We need an API that forwards keysyms as-is so they can be handled and passed on in the compositor (likely through wl_text).
Closing this, we'll investigate this when we have actionable requests from users for this type of feature.
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