You don’t seem to actually use inputs in your home.nix file so in principle you should be able to remove the

home-manager.extraSpecialArgs = { inherit inputs; };

line. Doesn’t hurt to keep it, though, if you think you may use inputs in the future.

The change you propose in 3 would not work the way you expect, the extraSpecialArgs needs to be set for Home Manager, not NixOS. My guess is that the nixosSystem function simply would ignore the extraSpecialArgs parameter.

Agree that there doesn’t seem to be anything weird here, the only suggestion I can add is that you could make it a bit more idiomatic by changing

home-manager.users.bs = import ./hosts/default/home.nix;

to

home-manager.users.bs.imports = [ ./hosts/default/home.nix ];

For many years now whenever I travel within EU I use my EU identity card and it’s very convenient. Would indeed be great if I could use something like it outside EU as well.

Finnish authorities are not investigating. The cable appears to just have been damaged by a digger.

That’s awesome and inspiring!