Reducing "suffering" without Buddhist meditation?

The bodhisattva Gambhiramati declared, “It is dualistic to say that voidness is one thing, signlessness is another, and wishlessness still another. What is void has no sign. What has no sign has no wish. Where there is no wish there is no process of thought, mind, or consciousness. To see the doors of all liberations in the door of one liberation is the entrance into nonduality.”

Vimalakirti Nirdesha Sutra

https://tricycle.org/magazine/dharma-door-nonduality/

If we agree that wishlessness does not suffer the stress of compound existence, then how do we then enter into nonduality? Without meditation, we could - perhaps - this is speculation - be able to in the sense of existing - seeing ourselves - not as a subject but outside time and space; in this sense, if some obligations are nondual, then even without meditation, maybe we can construct ourselves in response to them, and have our character be wishless etc., without that suffering.

Since unpleasing feeling are always related to unskillful actions, suffering-reduction starts much earlier and fundamental by virtue, goodwill (metta), the generosity and further.

Sila, based on metta, is the way of cure and what ever much "meditation" wouldn't fix the base.

As right view acts as the base, good to first of all heal one's ways of thinking, on and on, and in all circumstances, reflecting goodness and go toward gratitude:

There is the case where a certain person is not covetous. He does not covet the belongings of others, thinking, 'O, that what belongs to others would be mine!' He bears no ill will and is not corrupt in the resolves of his heart. [He thinks,] 'May these beings be free from animosity, free from oppression, free from trouble, and may they look after themselves with ease!' He has right view and is not warped in the way he sees things: 'There is what is given, what is offered, what is sacrificed. There are fruits & results of good & bad actions. There is this world & the next world. There is mother & father. There are spontaneously reborn beings; there are brahmans & contemplatives who, faring rightly & practicing rightly, proclaim this world & the next after having directly known & realized it for themselves.' This is how one is made pure in three ways by mental action."

— AN 10.176

Also useful to do not bypass the basic: The Healing Power of the Precepts

Second step, after perfect basic virtue, comes by reducing food, consume (8 precepts)

Third step goes toward sense restrain, higher virtue, reflecting the dangers and not taking on what ever touches.

Fourth step goes on with 24h knowing oneself (s doing): mindfulness in the four frames.

When this stage if complete, right concentration, after passing joy, satisfaction, happiness, comes along by it's causes already given, and leads by itself to highest liberation from suffering as well.

"Conditioned existence" refers to how things are put together — or fabricated, to use the Buddha's word — in the mind, by the mind. This is what matters, not how things arise and pass away in nature, outside of the mind. That's not a cause of suffering, but how we think about it is.

Ven. Sāriputta puts your three "types" of suffering slightly differently:

“There are these three forms of stressfulness, my friend: the stressfulness of pain, the stressfulness of fabrication, the stressfulness of change. These are the three forms of stressfulness.”

Sāriputta's three "forms" correspond to the three groups (delimited by semicolons) of stress described by the Buddha , except that the order changes here to change; pain; fabrication:

Birth is stressful, aging is stressful, death is stressful; sorrow, lamentation, pain, distress, & despair are stressful; association with the unbeloved is stressful, separation from the loved is stressful, not getting what is wanted is stressful.

But if you think about the list enough, you may see that fabrication (the third group) points to the origination of stress, and it's also key to comprehending stress.

And comprehending stress is the first duty of the first noble truth. Once you can begin to comprehend the stress created in / by your own mind, you will become more dispassionate, more detached, and suffer less from the process.

You asked for a way to reduce stress without doing meditation, I just gave you it. But if you want to really know for yourself, you have to watch your mind creating stress — that's the main purpose of meditation.

PS. The Buddha details the stress of fabrication in his explanation of not getting what is wanted:

“And what is the stress of not getting what is wanted? In beings subject to birth, the wish arises, ‘O, may we not be subject to birth, and may birth not come to us.’ But this is not to be achieved by wishing. This is the stress of not getting what is wanted. In beings subject to aging… illness… death… sorrow, lamentation, pain, distress, & despair, the wish arises, ‘O, may we not be subject to aging… illness… death… sorrow, lamentation, pain, distress, & despair, and may aging… illness… death… sorrow, lamentation, pain, distress, & despair not come to us.’ But this is not to be achieved by wishing. This is the stress of not getting what is wanted."