Hello

I cannot add vendor prefixes to my styles using autoprefixer and postcss.
It seems like autoprefixer and postcss are not working at all.

I'm using NextJS 14.1.4 with app router. I'm writing my css using modules.
I have added a browserlist entry in my package.json file.
I have also installed autoprefixer and postcss (along with some plugins)
In fact here's my configuration.

package.json

{
    ....
        "next": "^14.1.4",        
        "react": "^18.2.0",
        "react-dom": "^18.2.0",
    },
    "devDependencies": {
        "@types/node": "^20",        
        "@types/react": "^18",
        "@types/react-dom": "^18",
        "autoprefixer": "^10.4.19",
        "eslint": "^8",
        "eslint-config-next": "^14.1.4",
        "postcss": "^8.4.38",
        "postcss-flexbugs-fixes": "^5.0.2",
        "postcss-preset-env": "^9.5.4",
        "prettier": "^3.2.1",
        "typescript": "^5"
    },
    "browserslist": [
        "defaults and fully supports es6-module",
        "maintained node versions"
    ]
}

postcss.config.js

module.exports = {
    plugins: {
        'postcss-flexbugs-fixes': {},
        'postcss-preset-env': {
            autoprefixer: {
                flexbox: 'no-2009',
            },
            stage: 3,
            features: {
                'custom-properties': false,
            },
        },
    },
}

To test this i am doing npm run build and then I'm looking for vendor prefixed flex entries such as this one:

display: -webkit-box;
    display: -ms-flexbox;
    display: flex;

Can someone please help me.
Thank you !!