RE: U2414H, AC511 Soundbar, Sky Q Mini box, no audio?
I am not sure about the Sky Q Mini box. Dell never tested it. One way to test the U2515H HDMI + audio would be to plug a Windows based computer into the U2515H, then test for audio out of the AC511.
* AC511 plugs into the U2515H USB downsteam port * Computer USB port --> USB upstream cable --> U2515H USB upstream port * Computer HDMI out port --> HDMI to HDMI cable --> U2515H HDMI in port * Open the Windows Playback and choose U2515H HDMI as the Default Playback Device. If audio plays, then we know that the AC511 and U2515H are functional