: Ensure your SD card is formatted to FAT32 so the 3DS can read the directories quickly.
Since true cloud streaming is limited by the 3DS hardware, the most reliable way to "stream" your Spotify content is to download your playlists to a computer and transfer them to the console.
The 3DS’s web browser is terrible by modern standards—no WebGL, limited JavaScript, and only 6MB of reserved memory. However, there is a trick: used to have a "legacy" fallback mode.
The fact that a fully-featured, native Spotify client still doesn't exist for the 3DS isn't for lack of trying. It's due to some formidable technical barriers.