I'm so tempted to use GuixSD over NixOS. Honestly, Guix seems much more well-designed, non-myopic. It even has great documentation! The only two drawbacks are lack of packages (compared to Nix) and an arguably impractical puritanism about unfree software.

You can use nix packages in guix

I needed the latest adb, and it worked well and easy to flash my android phone

https://guix.gnu.org/en/manual/devel/en/guix.html#index-nix_...

Also you can add third-party unfree channels

I think both guixsd and nixos are very good, good documentation, single file with most of your system configs, easy to install and re-install, it looks different but it not difficult at all. Completely worth it

For adb you can get my channel too where I experiment with a new build system:

https://framagit.org/tyreunom/guix-android