Hmm, that is disappointing to hear…
I used to write a lot of software in a previous life, so I well aware of how common it is to underestimate the effort it takes to fix things.
Well, HifiberryOS is completely Free, Open source software so them using this unofficial client and API is 100% okay in my books.
But, what I really have trouble supporting is Volumio’s ambiguity w.t.r Spotify.
Volumio have both commercial hardware (primo,rivo,etc) and commercial OEM software where Spotify support is prominently marketed.
Spotify has clearly documented specific SDKs and APIs for such commercial hardware.
https://developer.spotify.com/documentation/commercial-hardware/implementation/reference/3.200/
There are multiple posts asking if Volumio has help from/uses authorised official SDKs from Spotify
E.g. @Josh2000
and @Fenrir999
But there has been no clear answer if(why) even the commercial offerings from Volumio use unofficial clients and not the official SDKs?