As you can see in my previous message's screenshot, I tried that, to no avail. I commented it out after I got the required hash, because my end goal is to figure out how to find cargoHash - I assumed you meant that cargoHash == cargoDeps.hash.

Here's the nix code copied in this time

diff --git a/home-manager/default.nix b/home-manager/default.nix
index ce1dfb5..278eef1 100644
--- a/home-manager/default.nix
+++ b/home-manager/default.nix
@@ -1,4 +1,4 @@
-{ ... }:
+{ pkgs, ... }:
 {
   imports = [
     ./machine-configs
@@ -7,6 +7,25 @@
     ./programs/gui
     ./programs/terminal
   ];
+  home.packages = [
+    (pkgs.kickoff.overrideAttrs (old: rec {
+      # version = "k900-demo";
+      # src = pkgs.fetchFromGitHub {
+      #   owner = "j0ru";
+      #   repo = "kickoff";
+      #   rev = "fe09c4cb2665cfd659844603ea7ade69d1827a3a";
+      #   hash = "sha256-V4MkVjg5Q8eAJ80V/4SvEIwjVy35/HVewaR1caYLguw=";
+      # };
+      # useFetchCargoVendor = true;
+      # cargoHash = "";
+      cargoHash = "sha256-XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
+      # cargoHash = "sha256-bkum6NOQL0LVsLvOmKljFHE86ZU3lLDR8+I3wL0Efmk=";
+      # cargoDeps = pkgs.rustPlatform.fetchCargoVendor {
+      #   inherit src;
+      #   hash = "sha256-bkum6NOQL0LVsLvOmKljFHE86ZU3lLDR8+I3wL0Efmk=";
+      # };
+    }))
+  ];
   home.sessionVariables = {
     DOTNET_CLI_TELEMETRY_OUTPUT = 1;
   };

Any rust toolchain tech people can figure out what is the actual issue in? The comments including newest one are kinda confused? I posted a fix that fixed my issue on the thread tho.

https://github.com/nix-community/fenix/issues/123