Install 2 packages as development dependencies (will be set to devDependencies in the same package.json that's used for the NextJS application): I realize we're having the same package.json file for the NextJS application and the nodeJS script - that's not an issue, just make sure that the nodeJS packages we're using for this upload functionality are saved as dev only.

npm i node-scp dotenv --save-dev

Create a .env file with the following details :

HOST="mydomain.com"
USERNAME="username"
PASSWORD="MyPassword"
PORT="22"
LOCAL_FOLDER="./out"
REMOTE_FOLDER="/home/myUsername/apps/myNextJSApp"

I am using OpalStack where each application's root path is pre-set to ~/apps/appName, so my REMOTE_FOLDER is /home/myUsername/apps/myNextJSApp - but for most other hosting companies, it'll be something like /home/myUsername/public_html

Next, create an upload.mjs file in the root directory as the NextJS app - we need to save the file as a .mjs file though since we can't set "type": "module" in package.json file which is being used by NextJS also. Enter into upload.mjs :

import * as dotenv from 'dotenv'
import { Client } from 'node-scp';

dotenv.config();

var remote_server =
{
    host: process.env.HOST,
    port: process.env.PORT,
    username: process.env.USERNAME,
    password: process.env.PASSWORD,
    // forceIPv4: boolean,
    // forceIPv6: boolean,
    // privateKey: fs.readFileSync('./key.pem'),
    // passphrase: 'your key passphrase', 
}

const upload = async () =>
{
    try
    {
        const client = await Client(remote_server);
        console.log("Uploading .... ");
        await client.uploadDir(process.env.LOCAL_FOLDER, process.env.REMOTE_FOLDER);
        client.close();
        console.log("Upload Done");
    }
    catch (e)
    {
        console.log(e);
    }
  }

upload();

Now edit the package.json file to include this :

"build": "next build && next export && node upload.mjs",

After you've tested your app via npm run dev, you can now run npm run build and it'll build and export followed by uploading your out folder (which is the default NextJS's build folder) to your server's NextJS path.