Thanks Spleen, curiosity got the better of me, just hooked my Steam Dock up to my office LG C1 and its working fine, no artefacts, sound all coming through. I do like it but its not quite there with Switch compatibility. The Switch just works whereas hooking a controller to the Deck is a mixed bag!
The old wired 360 works in SteamOS same with the Xbox 2013 controller, wired they are both recognised, only mapping in a game is the tricky part, the game is not recognising unless its a 'verified' game. To be fair I just threw it all together to see if the Dock works and it does. Haven't dabbled with wireless much as patience is in short supply, so will try again another time.
Just wanted to report that there is hope!