In case someone follows the same route using Volumio as Snapcast client - the writeup of @Burningstone is somewhat outdated. The combined snapcast client+server plugin for volumio does not work on Volumio 3 any more and it has been dropped the author in favor of separate client and servr plugins.
So you want to use this in the same way as described in the writeup: https://github.com/Saiyato/volumio-snapclient-plugin/issues