req.body undefined on get but not on post using axios and multer

I am sending user login and registration data with axios to my backend as get and post requests respectively, but I can't figure out why for the login (get) request, the req.body in express is undefined even though everything seems perfectly identical

In the react app I sent axios requests as shown:

const axiosConfig = {
headers: { "Content-Type": "multipart/form-data" }, // commenting this out and using defaults does nothing
};

function submitHandler(e) {
  e.preventDefault();
  const axiosUser = axios.create({ baseURL: "http://localhost:3100" });

  let userData = new FormData();
  userData.append("username", usernameRef.current.value);
  userData.append("password", passwordRef.current.value);

  if (formState === "login") {
    for (let pair of userData.entries()) {
      console.log(pair[0] + ", " + pair[1]); // username, x // password y as expected
    }

    console.log("LOGIN");
    axiosUser
      .get("/u", userData, axiosConfig)
      .then((res) => console.log("success:", res))
      .catch((err) => console.log("error:", err))
      .then(() => {
        navigate("/");
      });
  } else {
    for (let pair of userData.entries()) {
      console.log(pair[0] + ", " + pair[1]); // username, x // password y as expected
    }

    console.log("REGISTER");
    axiosUser
      .post("/u", userData, axiosConfig)
      .then((res) => console.log("success:", res))
      .catch((err) => console.log("error:", err))
      .then(() => {
        navigate("/");
      });
  }
}

In express, I parse the formData using multer upload.none() as my other routes do have image uploads to cloudinary:

const upload = multer({ storage }) // cloudinary storage

app.post(
  "/u",
  upload.none(),
  asyncErrorWrapper(async function (req, res) {
    const result = await User.findOne({ username: req.body.username });
    console.log(result);
    if (result) {
      console.log(req.body.username);
      return res.status(400).send("username already exists");
    }

    const hashedPw = bcrypt.hashSync(req.body.password, 10);

    const newUser = new User({
      username: req.body.username,
      password: hashedPw,
    });
    await newUser.save();
    console.log(newUser);
    console.log(`  > new user "${req.body.username}" created`);
    res.status(200).send("user created");
  })
);

app.get(
  "/u",
  upload.none(),
  asyncErrorWrapper(async function (req, res) {
    console.log("LOGIN");
    console.log(req.body); // ! undefined, {} if parsed with bodyParser
    console.log(req.body.username); // error, undefined with bodyParser
    console.log(req.body.password); // error, undefined with bodyParser
    res.send(req.body);
  })
);

I have tried removing axiosConfig which did not change anything, and using another parser like bodyParser in place of multer logs req.body as an empty object.