I would like to propose a feature:
In the source settings it should be possible to specify a snapcast server IP address. If the snapcast source is activated in the settings, it can be selected on the Volumio. Then the Volumio plays the music from the snapcast server.
This is already implemented natively in the multiroom dock. It uses the multiroom sync feature of premium.
Would this fit your use?
I already have this multiroom feature (premium user) and I am using this for some use cases. But for another case I have an additional snapcast server (not a Volumio) which I would like to add as source. 