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As an aside, don't bother with Sidequest right away.
I spent hours messing with it, getting custom songs installed for Beat Saber, etc. and found that the vast majority of custom songs are so bad that it wasn't worth the trouble.
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I disagree with this. If you are new to Beat Saber, then the custom songs can feel awkward as they tend to be more difficult than the standard songs. Once you get the hang of playing the standard tracks on Expert and Expert+ then the custom songs start to feel more natural and enjoyable.
With that said, there are quite a few trash-tier song mappings out there, you just have to keep an eye on the song user review scores.