Unable to load unpacked Chrome extension inside Linux container using Puppeteer or CLI

I’m trying to load an unpacked Chrome extension inside a Linux-based Docker container to automate extension testing. However, the extension does not load — neither when launching Chrome directly via CLI nor when using Puppeteer.

Environment Details

1. Base image: linuxserver/webtop:ubuntu-xfce
2. Chrome version: Google Chrome 142.0.7444.162
3. Dependencies from package.json

{
  "dependencies": {
    "puppeteer": "^24.29.1",
    "puppeteer-extra": "^3.3.6",
    "puppeteer-extra-plugin-stealth": "^2.11.2"
  }
}

4. Goal: Load unpacked Chrome extension for automated testing

What I have tried

1. Launching Chrome via command line

    google-chrome \
      --no-sandbox \
      --disable-dev-shm-usage \
      --disable-gpu \
      --user-data-dir=/config/chrome-profile \
      --load-extension=/app/extension \
      --disable-extensions-except=/app/extension

2. Using Puppeteer with --load-extension

const puppeteer = require('puppeteer-extra');
const StealthPlugin = require('puppeteer-extra-plugin-stealth');

async function runAutomation() {
  puppeteer.use(StealthPlugin());

  const browser = await puppeteer.launch({
    executablePath: '/usr/bin/google-chrome',
    headless: false,
    ignoreDefaultArgs: ['--disable-extensions'],
    args: [
      '--no-sandbox',
      '--disable-dev-shm-usage',
      '--disable-gpu',
      '--user-data-dir=/config/chrome-profile',
      '--load-extension=/app/extension',
      '--disable-extensions-except=/app/extension',
      '--remote-debugging-port=9222'
    ],
  });
}

runAutomation().catch(console.error);

This same Puppeteer code successfully loads the unpacked extension on my Windows machine.

However, inside the container, both approaches (CLI and Puppeteer) start Chrome in headful mode successfully — but the extension never loads.

Visual demonstration

Here’s a short recording showing how the script runs — the Chrome window opens, but the extension isn’t visible under chrome://extensions/. Video reference: https://www.loom.com/share/e567b06d03b24236b0a5f525170f5858

Verified Checkpoints

1. --user-data-dir=/config/chrome-profile exists, contains the unpacked extension, and has 777 permissions.

   1.1 I can manually load the same extension when using Chrome interactively (chrome://extenstions -> Enable Developer mode -> Load Unpacked)

2. Chrome launches correctly in headful mode.

3. Used ignoreDefaultArgs: ['--disable-extensions'] while launching Puppeteer to ensure extensions aren’t disabled.

4. Also tested with Chrome’s internal logging flags — but no error or clue found:

--enable-logging --v=1 --enable-extension-activity-logging

Questions: What am I missing or misconfiguring that prevents the unpacked extension from loading inside the container, even though it works perfectly on Windows?