HOLY COW!!

It friggin worked:

I added to my announcement model

public function testXY(){
    return $this->hasMany('App\Attachment');
  }

and replaced 'attachments' with testXY in my query like so:

$posts =       Announcement::with('comments', 'testXY')
                     ->orderBy('id', 'desc')
                     ->get();

And it echoed test 5 times, the number of attachments on that post. AWESOME! Interestingly, it echoes it regardless of whether I put 'testXY' or 'attachments' in the query. Looks like it accepts the class name or the name of the method in the model.

You are awesome!!!

Glad it got solved ☺