Apparently this is slightly old news (the Git commit timestamp is just over three months ago), but KWin, the KDE window manager/compositor, now implements the solution pioneered by GNOME for letting screen readers monitor and intercept keystrokes on Wayland, specifically, the org.freedesktop.a11y.KeyboardMonitor D-Bus interface. I prototyped this solution in GNOME last summer. Thanks to @npub1hl6m...hych for bringing it to production in GNOME, and now to Nicolas Fella for implementing it in KDE.