flysystem error message. Driver is missing
Requirements
If you look at the flysystem.install file (it's currently the same whether you installed 2.0.x or 8.x-1.x), you can see the code used for flysystem_requirements().
The general structure of the checking is as follows:

Validate the schemes in settings.php
Make sure the dependencies are installed:
a) League\Flysystem\Filesystem
b) League\Flysystem\Replicate\ReplicateAdapter
c) Twistor\FlysystemStreamWrapper
Then, it calls ensure() on the plugin for each scheme, and makes sure the plugin can be instantiated.

This 3rd step calls this code (src/FlysystemFactory.php):
  public function getPlugin($scheme) {
    if (!isset($this-&gt;plugins[$scheme])) {
      $settings = $this-&gt;getSettings($scheme);

      $this-&gt;plugins[$scheme] = $this-&gt;pluginManager-&gt;createInstance($settings['driver'], $settings['config']);
    }

    return $this-&gt;plugins[$scheme];
  }

It also provides the defaults:
  protected $defaults = [
    'driver' =&gt; '',
    'config' =&gt; [],
    'replicate' =&gt; FALSE,
    'cache' =&gt; FALSE,
    'name' =&gt; '',
    'description' =&gt; '',
  ];

Given the above information, your plugin and schema should have declared your driver with 'driver' =&gt; 'ftp'.
Solution?
Also, on the main module page under &quot;supported adapters&quot;, it says:

Ftp (Requires the ftp extension)

Though I'm not sure, since it doesn't link to another module like the other adapters, I think it means the PHP extension. Try installing the ftp PHP extension. Here's the page for setup instructions.