Audio does not seem to work out of the box for the Dell XPS 17 9700 NixOS (this also applies to most linux distros).

https://github.com/maaarghk/soundwire-dkms/commits/master seems to offer some sort of support for this, but I'm not entirely sure how to integrate this support into nixos.