ported the lua, port is complete, I think.

lua/lsp/nix.lua

@@ -0,0 +1,27 @@
+return {
+  {
+    "nixd",
+    enabled = nixInfo.isNix, -- mason doesn't have nixd
+    for_cat = "nix",
+    lsp = {
+      filetypes = { "nix" },
+      settings = {
+        nixd = {
+          nixpkgs = {
+            expr = [[import <nixpkgs> {}]],
+          },
+          options = {
+          },
+          formatting = {
+            command = { "nixfmt" }
+          },
+          diagnostic = {
+            suppress = {
+              "sema-escaping-with"
+            }
+          }
+        }
+      },
+    },
+  },
+}