Hi there and welcome!
First of all I want to give a small hint, when using flakes your channel related commands might not be doing what you expect them to do, aka they do no longer influence your system config.
You might want to set up your NIX_PATH to use the nixpks input of your flake, so that stable nix commands use the same nixpks revs like the unstable (flake) ones. In a “flake world” the inputs “replace” the channels (or in other words flake don’t use the channels)
About your issues:
When taking a careful look at your flake inputs, one will notice that there is no branch mentioned for the home manager input. That will result in picking the default one which is master and that matches up to nixos-unstable.
As your nixpks input is nixos-24.11 (so stable), that is the source of the error message.
As for your channels you tried to pick stable home manager, your should update the home manager input to
home-manager.url = "github:nix-community/home-manager/release-24.11"
That should update the flake.lock (as the URL changed) and the warning should be gone.