How to install an extension in Firefox-ESR?

Question

I created a simple extension and it is working when I am loading it manually via about:debugging. However, I'd like this extension to start automatically without having to load it manually.
Following the Deploying Firefox with extensions guide:

Step 1: Create directories In the Firefox ESR installation directory, you will need create some required directories. First, create a directory called distribution. Inside of that directory, create another called extensions.

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Step 2: Add extensions We now need to add our extensions into the extensions directory that we created above. This will require you to know the add-on ID for each extension that you wish to add to this directory.

To add the extensions to this directory, you should include the extension's XPI file. It will need to be renamed to the add-on ID, while being careful to keep the .xpi file extension.

In manifest.json I created an add-on ID as follows:

"browser_specific_settings": {
    "gecko": {
      "id": "tony@myext"
    }
}

And I copied the [email protected] to /usr/lib/firefox-esr/distribution/extensions. I closed Firefox and restarted it and the extension was not working (it is supposed to block access to a specific url which works when I load the extension manually).

Any ideas will be appreciated as the internet is somewhat sparse with terrible documentation...