First of all, Divine Sense does not mechanically detect “good or evil” creatures. It specifically allows you to locate any celestial, fiend, or undead within 60 feet of you. The first line of the description simply explains how the detection ability described in the following sentences is perceived in-universe by the paladin.

The Divine Sense class feature is described as follows:

The presence of strong evil registers on your senses like a noxious odor, and powerful good rings like heavenly music in your ears. As an action, you can open your awareness to detect such forces. Until the end of your next turn, you know the location of any celestial, fiend, or undead within 60 feet of you that is not behind total cover. You know the type (celestial, fiend, or undead) of any being whose presence you sense, but not its identity (the vampire Count Strahd von Zarovich, for instance). Within the same radius, you also detect the presence of any place or object that has been consecrated or desecrated, as with the hallow spell.

Given that description, I think that by the rules as written, Divine Sense would not detect beings on the other side of a portal, as they are not actually within 60 feet of you. At least, I have not seen anything to suggest that things on the other side of a portal count as being within a certain distance of you.

Though the rules don’t explicitly confirm or deny how distances are calculated with interplanar portals, rules designer Jeremy Crawford unofficially confirms how distances are calculated between different planes on Twitter:

If two people are on different planes of existence, they are infinitely far away from each other. For example, if I’m on the Material Plane and you’re on the Ethereal Plane, we’re not within 30 feet of each other.

In short, things on different planes aren’t really any specified distance from one another, but rather an infinite distance – there’s no way to calculate the distance between points on different planes.