So

diff --git a/pkgs/development/compilers/rust/rustc.nix b/pkgs/development/compilers/rust/rustc.nix
index d7a1ee625f9c..92e0997a3e19 100644
--- a/pkgs/development/compilers/rust/rustc.nix
+++ b/pkgs/development/compilers/rust/rustc.nix
@@ -161,6 +161,7 @@
             # Other targets that don't need any extra dependencies to build.
           ]
           ++ optionals (!fastCross) [
+            "bpfel-unknown-none"
             "wasm32-unknown-unknown"

             # (build!=target): When cross-building a compiler we need to add
diff --git a/pkgs/development/python-modules/mitmproxy-linux/default.nix b/pkgs/development/python-modules/mitmproxy-linux/default.nix
index 01bacdb002ed..0ee05f35dcb4 100644
--- a/pkgs/development/python-modules/mitmproxy-linux/default.nix
+++ b/pkgs/development/python-modules/mitmproxy-linux/default.nix
@@ -18,6 +18,13 @@
     tag = "v${version}";
     hash = "sha256-lWUHdS+AkMnIg+1SR+9fC+YjcyLK80UknwGablniLSg=";
   };
+
+  postPatch = ''
+    substituteInPlace mitmproxy-linux/build.rs \
+      --replace-fail '"-Z",' "" \
+      --replace-fail '"build-std=core",' ""
+  '';
+
   cargoDeps = rustPlatform.fetchCargoVendor {
     inherit pname version src;
     hash = "sha256-ihbVh73eulqFyKC49KfsCFJqahr3nWVFFc97iFFf3Nk=";

will not just work?

rustc> Documenting stage2 library {alloc, core, panic_abort, panic_unwind, proc_macro, std, sysroot, test, unwind} in HTML format (aarch64-apple-darwin -> bpfel-unknown-none)

so it's the docs after all

In reply to @sandro:supersandro.de
Someone wrote earlier that we could compile the mitmproxy-linux-ebpf crate separately. I could do that probably by copying things from rust-hypervisor-firmware but I am a bit lost how to integrate that back into mitmproxy-linux

but the advice in the manual says use crossSystem. I tried doing roughly this:

      rustTargetOverride = {rust.rustcTarget = "aarch64-apple-ios";};
      crossSystem = (lib.systems.elaborate "aarch64-darwin") // rustTargetOverride;

My rationale being "I just want to change the target for rustc"