There is currently a lot of confusion around getting the Sonos ARC setup with LG tv's. Most of this discussion is around the eArc connector support and whether your specific model of LG TV will output Dolby Atmos.
For the purposes of this post I just want to focus on one thing - the LG Magic Remote.
The TL;DR here is that you need to re-run through the soundbar setup on your TV - it's nothing to do with the Sonos app.
Both of my monitors are 1080p 24" screens. One is a Samsung LCD display and one is a LG LED display. Both use HDMI to connect to a source. At present there does not appear to be any dual HDMI usb 3 docks out there. They all have 1 HDMI and 1 DVI slot so I had to purchase a HDMI to DVI connector on Amazon for about £5 to make sure I could hook up both monitors to the hub.
I've been using it this dock now for over a month so I thought I'd write a quick review for anyone interested.