Then please share how your system is configured connection wise, and all your U22 XJ android audio settings and kodi audio settings so that we can all benefit from your success.
Connected by HDMI only. In MINIX Settings - Audio Output set to Manual and all the various sound formats enabled.
I'm using the pre installed version of Kodi, in audio settings - Allow Passthrough, enable the four settings below that including Enable Dolby Digital (AC3) transcoding (which I believe is the key) and away you go with multi-channel audio.