Unlike the standard Galaxy S4, the headphone jack on the S4 Active is attached to the midframe instead of the mainframe.

All removable flex cables will have an access slot to get a tool (I use a sewing needle) underneath the adhesive and pry it up.

Once this is done you can remove whatever component is attached to the flex cable. In this case it is the headphone jack.

Always remember to be gentle with the flex cables to avoid rips and tears.