https://www.theverge.com/circuitbreaker/2017/9/14/16309196/essential-phone-headphone-jack-module-announced

A headphone jack might not have been essential enough to be part of the Essential Phone itself, but the company has confirmed it’s working on a module that includes one. “We are actively developing a high end audio accessory to support a 3.5mm jack,” the Essential team said during a Reddit AMA today.

Aside from the 360-degree camera, customers can next expect the charging dock to be released before future modules including the high-end audio device. In a follow-up remark, another Essential employee said ”our head of architecture is in Asia right now getting our high-end audio accessory super dialed. He graciously called me at 3AM today so we could talk about some specifics for our design.”