Google Home, Amazon Echo, Apple HomePod, Sonos One, that thing that JBL put out; the once-gimmicky smart-speaker market is pretty crowded now, but all of my research suggests Subsonic is still mostly unsupported. I know it has to do with a lack of OAuth2 support and I get why, but there are other serving platforms (Plex, Kodi, Asitga, etc.) that fill this gap. I don't want to have to move away from Subsonic, though.
