Someone recommended QuitMormon. That's an option, but Kirton McConkie, the church's law firm, handles those resignations, and they've been slow walking those resignations for the past couple years. We're talking months, sometimes between submission and confirmation.

Another option, which will probably be faster, is to send your resignation in to the Data Privacy Officer at Church HQ. This is the route through which European GDPR resignations are processed (GDPR legislation has teeth), so the church doesn't screw around with these resignations like they might with some others.