IBus provides the fixed allowlist of XKB engines in
ibus-setuputility can show the XKB engines indicated in only that file in non-GNOME desktops. (gnome-control-center shows XKB list from gnome-desktop3 in GNOME desktop instead.) IBus 1.5.23 builds the
simple.xmlwith a denylist internally and the file includes most of XKB engines likes 'gb'.
IBus 1.5.23 will show glyphs from the input method’s language in non-GNOME. E.g. U+76F4 ("直") has different glyphs in Japanese and Chinese and the preivous IBus shows the glyph with the desktop' language instead of the input method’s one.