While you can’t directly pair the FTV voice remote with an Echo device, you can use it to control one. For example, I have a Dot that I use to play music named “Downstairs”. These commands work (though I have to be within range of the FTV that I’m paired with).
“Play Bruno Mars Downstairs”
“Volume 4 Downstairs”
“Next song Downstairs”
If you omit the word “Downstairs”, then the action will occur on the FTV. Alas the track and pause buttons on the remote will only control the song when playing through the FTV, but it’s still nice to get some of the functionality without springing for an Alexa remote.