So I don't think positions like existentialism exist in Buddhist philosophy. I say this because the whole framing of causality is fundamentally different in Nagarjuna's treatise of dependent origination, so one doesn't actually cause meaning (in the traditional sense)
What were the Buddhist schools of thought that originated for the human pursuit of meaning? (I would be interested in overviews between different schools of Buddhist thought).
Disclaimer: I'm not a Buddhist, but I'm somewhat familiar with Zen Buddhism.
Buddhism is about liberation from suffering by letting go of attachments to the material world. According to Buddhism, the material world is an illusion and we shouldn't be concerned about what goes on in it. Getting attached to stuff happening in the material world only causes us stress and suffering, and for no reason, because (according to Buddhism) it is an illusion.
Existentialism, in contrast, says that we should make our own meaning, which is to say that we should find something in the world and decide that this is the reason for our life. In the Buddhist perspective this is only attachment, and harmful; why should that particular part of the world be so important? It only causes suffering to attach yourself to something in the world. Buddhists say this even extends to interpersonal attachments; we should avoid excess attachment even to a friend, family member, or romantic partner. Buddhism is like Stoicism in this regard.
However, Buddhism does not say we should just withdraw from the world entirely. It advocates the practice of loving-kindness towards all living things (without attachment to any living thing in particular), and following the Eightfold Path.
Camus thinks we need to find meaning in this life, otherwise we have no reason not to just kill ourselves. The Buddhist answer to this is that if you killed yourself you would just reincarnate and continue suffering, so it is no escape.
I don't want to say that Buddhists think the "meaning" of life is to free yourself from the cycle of attachment and suffering. If you practice Zen in order to achieve something else, even if that something else is "enlightenment" or "freedom from suffering," then you are wasting your time. Because, you don't want to get attached to the idea of enlightenment or the idea of freedom from suffering. That's harmful attachment that causes suffering if you fail to achieve what you wanted, just like being attached to something in the material world. The purpose of Zen is just to sit, and that's all.
If you are trying to attain enlightenment, you are creating and being driven by karma, and you are wasting your time on your black cushion.
- Sunryu Suzuki
But, Buddhism in general is oriented towards freeing oneself from attachment and suffering, even if doing so with purposeful intent is the wrong state of mind.
I don't think Existentialism depends on a framing of causality. It's about putting a personal confrontation with the conditions of existence in the primary position, summarised by Sartre's aphorism "Existence before essence." Which, I'd call extremely compatible and consonant with Sunyata and the Three Marks of Existence, especially Dukkha. There is a tendency to see Existentialism as basically pessimistic, and Buddhism as cheerful, which I think obscures their similarities.
The first task in addressing this question is how to translate 'meaning' into a Sanskrit term.
Dharma means 'the way' and 'truth', and the path of virtue and the correct way of living if we attend to the true nature of the world. In Buddhist thought that means understanding the true nature of ourselves and the world, and so coming to act so as to cease to cause (unnecessary) suffering, which is to achieve 'unshakeable liberation' from suffering, or awakening. For Therevada Buddhism the job is to become an Arhat, and just stop causing suffering. For Mahayana and Vajryana Buddhism the highest job is to continue to accept causing suffering, in the service of the Bodhisattva path and emptying the hells.
Someone on the Buddhism Stack Exchange helped me out with 'artha' being the most direct Sanskrit translation for meaning. But we can see from the meaning of the title of the Hindu Arthashastra, that this isn't a perfect fit either (here it's described as indicating 'science' or 'craft'). From that Wikipedia link: "In an individual's context, artha includes wealth, career, activity to make a living, financial security, and economic prosperity. ... At the government level, artha includes social, legal, economic and worldly affairs." Which I'd say chimes strongly with the Eightfold Path, which Buddha described as the core of Buddhism and the essential teaching to reach Buddhist awakening. I'd say we should understand that Buddhist stance, as relating to the Hindu discussion of Artha Karma and Dharma, like in the Mahabarata which advocates we need a balance of focus on these, which I'd relate to skillfulness, conditions, and insight into truth respectively, in this context.
It's worth reflecting on how slippery the term 'meaning' is in Western thought, whether it's applied to the correct use of words, or how to live. On the origins of meaning: According to the major theories of concepts, where do meanings come from? On constructing a meaningful life: What are some philosophical works that explore constructing meaning in life from an agnostic or atheist view? I'd relate the core of meaning as situating ourselves towards information and knowledge, in a kind of 'personal cosmology' which locates us personally, in what we experience, and attempts to make a picture relating large and small, long and short term aspects of life-related to us. The core Existentialist confrontation and dissatisfaction, I would relate to the fact that as individuals pursuing gratification, our lives will cease to have meaning with the cessation of our bodies. And I'd relate the core purpose of spiritual and philosophical work to find meaning in life, as to latch on to worthwhile tasks and ideas that will outlive us. See: Exploring philosophy behind "Catch-22" novel: individual in war
Non-identification features significantly in the “human pursuit of meaning” in the concept of Maya.
'Non-identification even with the attainment of the base of neither-perception-nor-non-perception has been declared by the Blessed One; for in whatever way they conceive, the fact is ever other than that.' MN 113 Sappurisa Sutta
The same is repeated by Heidegger, leaving the conclusion to the reader.
“the clearing is pervaded by a constant concealment in the twofold form of refusal and obstructing. Fundamentally, the ordinary is not ordinary; it is extra-ordinary, uncanny [un-geheuer]. ... Truth, in its essence, is un-truth. We put it this way emphatically to indicate, with a perhaps off-putting directness, that refusal in the mode of concealing is intrinsic to unconcealment as clearing." The Origin of the Work of Art (GA5) p.31
So meaning grasped will be Maya, and the Tao that can be told will not be the true Tao; the reader is free of meaning.
In classic Buddhist fashion, I'll present this quote with no context:
“Paradoxical as it may seem, the purposeful life has no content, no point. It hurries on and on, and misses everything. Not hurrying, the purposeless life misses nothing, for it is only when there is no goal and no rush that the human senses are fully open to receive the world.”
Alan Watts
It gets to the heart of it, IMO.
I would humbly suggest that all Buddhists, at least all monastics, seek liberation, be that from suffering, rebirth, attachment, ignorance, or however that is framed. Does that suffice for a "meaning" to life? Absolutely, I think, and freedom is a central concern of much philosophy, political and existential and ethical.