Safety and privacy of using a third party app or website to transfer a Spotify library to Apple Music?

So full disclosure, this is more of a hypothetical question more than anything. I’m happy using Spotify, but, I do wonder what would be the easiest way to transfer my years worth of music from Spotify to Apple Music in an easy way. I looked into it and I’ve seen some apps or websites. Some that come to mind is TuneMyMusic, SongShift and/or Free Your Music

What are the privacy and safety dangers of using services/softwares like these to transfer …

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