Soulseek is the only "FOSS" solution. It's literally piracy though. There's no real free or open source way of getting licensed music. That's the whole point of copyright and royalties.
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I buy physical media (CD, vinyl, cassette). The CDs get ripped to flac and I use Soulseek to download flac versions the of vinyl and cassettes. I listen to the physical copies at home and use Plex/Plexamp when I'm out.
Congratulations! Depending on the country, you can either be considered a pirate or be in a legally gray area.
On Android, I like Spotube. You can sign into Spotify if you want, and the app will interact with it, but uses YouTube as the source for streaming the audio. This is good if, say, you have a free Spotify account and aren't at your PC to use the web player + uBlock.
I'm not sure there is any. The nature of copyright makes it so it's impossible to stream music without paying a lot of money to the three or five megacorporations that own all the music in the world.
The only FOSS way to do it will be by sailing the high seas
I use Blokada on Android and it blocks all the ads I would normally get on Pandora.