As you have the Beam connected to the TV using HDMI-ARC,  the TV and probably each of the HDMI connected peripheral device ‘remotes’ can control the Beams volume etc; using the HDMI-CEC protocol. 

You can also control the Beam with one remote ‘only’ (at a time) using infrared ..and that ‘remote’ setup can be done from the Beam’s room settings in ‘Settings/System/âBeam Room Name]’ in the Sonos App - just look for ‘Remote Control Setup’ - note though this is for infrared remotes only. It has nothing to do with the ‘remotes’ that are using CEC with your TV.

More info here re: CEC control:

https://en.wikipedia.org/wiki/Consumer_Electronics_Control

Ken you seem to be saying if I understand correctly that my URC universal remote should be able to work with app remote setup. Also since the Beam 2 is connected via the eARC the Samsung tv remote should continue to work.

Does that also mean if I were to connect a DirecTV receiver via HDMI to the TV… then the DirecTV remote would automatically control the Beam 2?

In your case if you can control the TV’s Volume by any means, the TV can pass this control through CEC. You can also train BEAM to respond to IR Volume control commands. This could be IR sent by the MX-350 or a TV or DirectTV remote that has been configured to control an A/V receiver using IR.  Most A/V control schemes are based on configuring the TV (Blu-ray, DVD, DirecTV, etc.) remote to control a specific A/V receiver model. The actual model number is arbitrary, simply give the same model for all of the remotes and avoid using the number of a nearby A/V receiver.

Yes, the Beam can use just one set of infrared remote control commands only - so if you had two remotes that were programmed with the same IR codes, both would work to control the Beam, post setup in the Sonos App - if the two remotes had different IR codes, then you can only setup one (or the other) to work with the Beam.

With CEC control - as long as the remotes ‘receiving’ device (a Fire-TV stick, for example) has CEC enabled and is connected to the TV, then the volume controls on its ‘remote’, which maybe Infrared/Bluetooth/RF-linked etc; to the Fire-TV stick, can of course pass-through the HDMI-Input to control the volume level on the TV and that is passed through to the Beam by the TV, using the CEC protocol too.

Hope that explanation assists further.

Thanks I believe I understand everything now… if not I’ll be back! Lol