You should switch to NixOS. I use NixOS by the way. ๐ ๐ ๐ ๐ ๐
This is the way. Iโd like to be a mod here.
Since this is federated and quasi-anonymous, there isn't and never will be a dispute resolution department. Both seller and buyer must take extraordinary measures to prevent scamming. That's why I highly recommend local pickup/exchange. Meet in a busy public place and wait for the funds to clear your wallet before you let the person walk off with your gear.
I think you should try NixOS first since GUIX is still a LOT more experimental. I am sure you could handle it coming from Gentoo but I think you'll find that the nix language is SUPER simple to pick up. It's basically like JSON.