[BUG] Method not implemented error when using jsonrpc

[devhl-labs]

Describe the bug

I just migrated from an old version of libreelec to this version https://releases.libreelec.tv/LibreELEC-RPi4.aarch64-12.0.0.img.gz
Now when I make a jsonprc request, I get a 501 error. Am I doing something wrong, or is this a bug?

const showNotification = {
    "jsonrpc": "2.0",
    "method": "GUI.ShowNotification",
    "params": {
        "title": "AutoPi",
        "message": `Playing: ${request.play}`,
        "displaytime": 15000
    },
    "id": 1
};

const url = `http://${ip}:${port}/jsonrpc`;

fetch(url, {
    method: 'POST',
    body: JSON.stringify(showNotification),
    headers: {
        'content-type': 'application/json'
    }
})
    .then(function (response) {
        console.log(reponse);                // 501
        return response.json();
    })
}