Is Spotify connect still working [will it keep on working]? I thought they'd have [were about to] drop the old API implemented by librespot (et al.) in favor of a pure web API?
I don't know exactly what volumio are doing. But librespot itself does currently still work. Who knows for how long (I doubt Spotify themselves know what they are doing). Librespot is transitioning to the new API, that API has already been implemented by other ports e.g. Librespot-java (and psst). It's not a pure Web API. It's a messy mix.
Volumio is ok, but I much prefer moodeaudio.org. It is also open source.
Volumio is pretty good. I used the free version. I've moved to Roon and it is on another level. Check it out if you would like to rediscover your music collection.