How to get Widevine DRM working in Firefox (Aarch64)?

Help
1

I did some looking up but didn’t find a clear way to do so. I want DRM enabled by default in all Firefox profiles if possible.

2

from widevine-cdm: add aarch64 support by RossComputerGuy · Pull Request #343393 · NixOS/nixpkgs · GitHub :

  nixpkgs = {
    overlays = [
      (final: prev: {
        firefox = prev.firefox.overrideAttrs (old: {
          buildCommand =
            old.buildCommand
            + ''
              mkdir -p $out/gmp-widevinecdm/system-installed
              ln -s "${pkgs.widevine-cdm}/share/google/chrome/WidevineCdm/_platform_specific/linux_arm64/libwidevinecdm.so" $out/gmp-widevinecdm/system-installed/libwidevinecdm.so
              ln -s "${pkgs.widevine-cdm}/share/google/chrome/WidevineCdm/manifest.json" $out/gmp-widevinecdm/system-installed/manifest.json
              wrapProgram "$oldExe" \
                      --set MOZ_GMP_PATH "$out/gmp-widevinecdm/system-installed"
            '';
        });
      })
    ];
  };

I have not tried this (on my todo).