The rules don't say a human gets a penalty to (or even Disadvantage) to a perception check made at a distance. Yet I submit nobody has any issues adjucating such a situation, except possibly you, and even then probably to create a problem with my suggestion that really isn't there.
Just like a human can get penalties even in broad daylight, obviously an elf can get them under a full moon.
Otherwise abilities such as Barbarian Eagle Totem means nothing.
Your claim that you are prevented by the rules from applying disadvantage to low-light vision at night outdoors is just as feeble as it sounds like.
Sure, you've made up your mind not to use my suggestion (and what your business in this thread even is, well probably never know!)
But don't make my suggestion out to be problematic when it isn't.
I'm suggesting that what worked perfectly before can easily be used in 5th edition. [emoji2]
I'm saying that 5th edition made changes that themselves are the cause of the OPs case.
So maybe the simplest solution is to get rid of those changes? [emoji3]
I make no claim that the rules prevent me from anything, nor have I stated that I have any issue adjudicating such situations.
My "complaint" is simply this: If using the 3e/4e rules for low-light vision, at what level of lighting does a creature with low-light vision suffer the effects of "dim" light?
That is, where they can still see but (in 5e terms and rules) they have disadvantage in the same way that a PC with normal vision does in dim light, or a creature with darkvision has in darkness?
Regardless of your answer, you probably don't care. Hey, whatever. From a game design standpoint, and a logical standpoint. it just makes sense to me that as the level of light decreases, there is a point where a creature with vision can still see, but not see as well as they do when in "bright" light, whatever the level of brightness is. It's not complicated, it's simply that there's a continuum that's consistent in the other types of vision from "no penalty" to "penalty" to "I can't see a damn thing." For a creature with darkvision, the step between the last two is magical darkness.
In the 3e/4e approach, the only creatures that have that step are those that have "normal" vision.
My business here is the same as yours and everybody else's here - to provide my opinion and thoughts on the question/rules at hand.
The two simplest solutions would be to either, 1. remember the rule, or 2. eliminate the penalty for creatures with darkvision in darkness (which the OP specifically stated they didn't like).
Your solution not only eliminates the penalty for creatures with darkvision in darkness (which the OP stated they didn't like), but it also suggests they add another type of vision, and assign it to either just PCs, or perhaps PCs and many other creatures.
Regardless, it amounts to 1. Change one rule to something the OP doesn't like, and 2. Add more rules that you might forget. So no, I disagree that it's the easiest solution for the OP, and really for new players. It is the easiest solution for people switching over from 3e/4e because it's what they are used to.