Discord is a free app that runs on all platforms (Windows, Mac, Linux, Ios, Android). It is organized into "Servers". The Oathsworn has one (thanks Mae!) as do most kins and groups. Within a server, it has both chat and voice channels, and is the app basically everyone uses to communicate in LoTRO.
1) Install on your PC, even if you don't have audio. Why? Because it's much easier to navigate on your monitor, and makes chat much easier to type. Also, people will put the URL into chat to invite you to a new server, and it is much easier to click than to type it into your phone. It can show who is talking within LoTRO (although there is a nasty bug that you have to reset each time you run LoTRO). It can also read chat messages in the selected channel to you.