Here is the definitive answer: Despite the information and mis-information appearing on websites operated by retailers, consumer magazines, Internet-based reviewers, and even this LG-operated site, it is clear that the Model 32LN530B has NO headphone jack, 3.5 mm or otherwise.
Furthermore, although some sources mention the connectivity with a "component receiver," be aware that such connectivity is limited to digital means. There are no RCA-type line-level analog output jacks. Thus, if your intent was to connect to your older stereo receiver, you are out of luck.
A further, but unrelated displeasure: There apparently is no over-the-air DTV signal strength indicator. It is extremely helpful for aiming the antenna, and is critical in the case of distant-station reception. Even the absolute cheapest Vizio sets have this feature, so its absence in this LG model is a very unpleasant surprise.