Redirecting output with Alexa skill to different device

I would like the ability to redirect the output to a specific Alexa device after sending a request to Plex via the Alexa skill.
For example:
"Alexa, ask Plex to play music by on living room Alexa. (Assuming the living Room Alexa is not the one that heard the command)
Right now, it accepts the command but only plays on the Alexa device that actually heard the command.
I was told by a developer (not Plex) that Amazon limits this option to only Amazon although I don’t believe this is true because it works for the IHeartRadio and SiriusXM skills that I know of so far.

My issue is similar - I’m trying to get multi-room playback to work.

What I’ve tried, that’s not working, is:
Alexa, ask Plex to shuffle playlist Christmas favorites everywhere.

The playlist name is “Christmas - Favorites”.
The speaker group is the default “everywhere” with my 2 speakers selected.
I think maybe she’s confused that “everywhere” is part of the playlist? But she doesn’t complain.

I’m thinking I just don’t have the right syntax. That command will shuffle the playlist on the Echo device that heard the command.

I checked these resources but didn’t find anything that helped.
https://support.plex.tv/articles/115000320808-getting-started-with-alexa-voice-control/
https://support.plex.tv/articles/236324808-alexa-voice-commands/