Based on Danny’s cue, I put together a system with:
Raspberry Pi 3 B+
HifiBerry Digi+ Pro HAT
RoPieee RoonBridge
It works great wired to the Devialet Phantom (ethernet>RoonBridge> SPDIF>Phantom). I have the Devialet remote control and it works perfectly. In fact, Roon volume control is set to Device and the remote is now very responsive. Before I had AirPlay driving the Phantoms. Roon volume was also set to Device, but there was a lot of lag with the remote control. It works much better now.
Thank you Danny!