Amazon's free, ad-supported music tier is no longer confined to Alexa devices. The service is now available through the Amazon Music app on Android, iOS and Fire TV for listeners in the US, UK and Germany. You're still limited to listening to playlists and stations (based on artists, eras, genres and songs), but this makes it trivial to check out the latest rap tracks or queue up holiday songs.
As with the initial launch, this is really about Amazon taking advantage of its far-reaching presence to bring more people into the fold. In theory, you'll like the free service (or dislike the ads) enough to pay for a Prime membership or a full-on Music Unlimited subscription. Whatever it costs Amazon in the short term might be worthwhile if it leads to more paying members.