The JPS Bible Commentary on Ecclesiastes has several interpretations of Hevel (הבל) on page xix which you can see for free. They go with "Utter Futility." A kind of hopelessness statement. There is some very good commentary on that page there.
But I think this is one of the central theological concepts of the text and that it solidly maps into the New Testament intepretation of the Character of Jesus.
Cain and Abel (הבל)
I think that this term is a central concept in the biblical text. One thing to note that it is exactly the name of Cain's brother in the Cain and Abel (הבל) story in Genesis 4. I get the sense that these two stories are related quite closely. If all human endeavors are utter futility and empty of merit and value, then we might understand the Cain and Abel story a bit differently.
If there is a core philosophy that all human actions are without value or merit then we see that Cain had all the merit. He was first born and was doing the right job (tiller of the land, as God had commanded in Genesis 3:23). Cain brings the first offering from his crops. Abel (hevel) shows up after and offers his first born from his flock, and God's gaze lands on Hevel and his offering and disregards Cain.
If we read Abel's name through the lens of Ecclesiastes, we see that God's gaze lands on Abel because he is truth. Cain is lost in the delusion of value/merit (the knowledge of good and bad - sin). There is a symmetry between Genesis 4 and Ecclesiastes. For example, in Ecclesiastes 3:14 we have, "I know that whatever God does endures forever; nothing can be added to it, nor anything taken from it;" In Genesis 4:2, we have "She [Eve] added and bore his brother Abel." This is the first instance of the word for "addition," יסף, which is also the basis for Joseph's name later in Genesis.
So in the logic of Ecclesiastes, "nothing can be added" an "Eve added Abel." We might then think of Abel as nothing. Empty. In fact, the JPS Genesis commentary notes that Abel's name appears exactly seven times in his narrative here, the number of completeness. And it is always contrasted with Cain who's name comes from "purchasing or getting or grasping." Abel is always described as "his brother" as if Cain possesses him, and never the other way around. There is this sense that Abel means non-grasping. Abel gave his first born of his flock. He is empty, meaningless, complete.
I know this sounds weird, but there are many parallels here between the character of Jesus in the New Testament. Jesus is the empty shepherd. He is, in Philippians 2, emptied. In John 5:19, "the Son can do nothing on his own, but only what he sees the Father doing." There is a kind of transparency of Jesus that reveals God.
Relationship to Kenosis
There is also a lexical overlap between the hebrew word ריק (reek). The two words are connected through their meanings of emptiness, but also through the septuagint's usage of overlapping greek terms κενός and μάταιος (entry in Trench's Synonyms of NT). This connects this term up to a broad range of related ideas in the New Testament interpretations of Jesus as well as to stories like the narrative of Gideon's army who held up ריק pots with torches inside and smashed them to reveal the light. One might view these as equivalent to the crucifixion where Jesus smashed his empty pot (his body) and revealed God's light. The warriors in Gideon's narrative (Judges 7) are characterized as obedient dogs.
The Knowledge of Good and Bad
Especially compared to the story of Gideon, the Exodus to Promised Land narrative, and the story of Cain and Abel, we might see that the bible has a running theme of emptiness and obedience.
This is in contrast to an ethical interpretation of the Bible. Instead of finding ethics in the book, we might see it as a narrative of obedience. The problem in Eden could be that we acted in disobedience to God's command and internalized the idea of Ethics and judgment.
In fact, In Numbers 13, God commands Moses to enter the promised land, but instead, he sends in spies to see if the land is good or bad and any number of attempts to judge it. It is these people who cannot enter. It is only the children (Deuteronomy 1:39) that may enter because they do not know good from bad. There is a sense here that may be mapped into first century Jewish interpretations of Jesus's comments that we must be as children, and not judging, to enter the kingdom of heaven.
So in this sense, one interpretation of the biblical text is that we must be empty of agency/ego to enter into paradise. This can be interpreted as seeing the emptiness of all the world around us. Paul says "hope all things" in 1 Corinthians 13, he doesn't say "hope a specific thing." It is when we try to control the outcome of things and don't yield control to God that we suffer.
It should be noted that there is a fundamentally different conception of the hero in the Hebrew narrative. Joshua, the ultimate guide into the promised land in the Torah, is one who is characterized (along with Caleb, whose name means "dog") as utterly following the Lord. He didn't try to make his own judgments like the other 10 spies.
The 300 dog like warriors in the Gideon story (Judges 7) had no weapons, and were selected from 32,000 israelites exactly so that it would be clear that God did it, and not the israelites. They were EMPTY of merit in this. They had no swords, just trumpets. They fought the midianites (name means "with judgment" - perhaps referring to the knowledge of good and bad). When the 300 blow their horns and smash their empty (ריק) pots, the midianites (who have all the swords - live by the sword) die by the sword.
Compare this to the 300 Spartans of the Greeks who lived on their own merit and by their own sword. They were led by Leonidas (the lion) and were contemporary to the Gideon story - and fought the Persians who had liberated the Hebrews from Babylon. And Ecclesiastes has this fascinating line:
Ecc 9:4, ...for a living dog is better than a dead lion.
The hero in the Bible is one who is obedient, rejecting his own concepts of good and bad. He is utterly obedient to God (as a dog). He illustrates God's agency and not his own. That seems like a good definition of emptiness.
I understand through the lens of determinism. I believe that there is no free agency in any of us, but it is our condition to think that we do have free will. This false idea that we have merit is the basis of our condition, but in fact, there is no merit (maybe "only God is good" - Mark 10:18). If we believe we have merit, but we don't actually have merit, then we might understand the biblical narratives call for obedience and non-judgment as a call to realize a fact. We are not in control. We are obedient perforce, but the suffering we have comes from not realizing this. Hence why it is not helpful to judge those who act in apparent disobediently (as if they are free agents).
We might take this and apply it to the meritocracy that makes up the western economic systems or really any human system and say "nope, that's actually empty - hevel." Whenever anyone claims merit or pride in their own accomplishments, we might say "nope, that's empty."
This is peculiar because most religious interpretations see the bible as an ethics text. Like it is a place we can turn to find the knowledge of good and bad to bolster a human merit system. But it really contains a theology of emptiness (הבל). All is hevel. Abel is an empty shepherd who is complete and God's gaze is fixated exactly because he has no merit and is empty. God's gaze lands on truth. Then throughout the text and into the New Testament we have Jesus, a reiteration of the narrative of empty shepherd. The bible is not an ethics text as I see it.