Look I don’t think even form jhana is necessary for enlightenment let alone formless jhana for example buddha said these
When you do truly know and see the eye, sights, eye consciousness, eye contact, and what is felt as pleasant, painful, or neutral that arises conditioned by eye contact, you’re not aroused by desire for these things.
Someone who lives unaroused like this—unfettered, unconfused, concentrating on drawbacks—disperses the the five grasping aggregates for themselves in the future. And their craving—which leads to future rebirth, mixed up with relishing and greed, looking for enjoyment in various different realms—is given up. Their physical and mental stress, torment, and fever are given up. And they experience physical and mental pleasure.
The view of such a person is right view. Their intention is right intention, their effort is right effort, their mindfulness is right mindfulness, and their immersion is right immersion.
“Mendicants, there are these seven prerequisites for immersion. What seven? Right view, right thought, right speech, right action, right livelihood, right effort, and right mindfulness. Unification of mind with these seven factors as prerequisites is called noble right immersion ‘with its vital conditions’ and ‘with its prerequisites’.”
And what is the faculty of immersion? It’s when a noble disciple, relying on letting go, gains immersion, gains unification of mind. This is called the faculty of immersion.
This vinaya story is about a guy without form jhana who attains arahantship
At that time in Benares there was a son of a good family called Yasa, the son of a wealthy merchant, who had been brought up in great comfort. He had three stilt houses: one for the winter, one for the summer, and one for the rainy season.
While Yasa was spending the four months of the rainy season in the rainy-season house, he was only attended on by female musicians, and he did not come down from that house. On one occasion, while he was enjoying himself with worldly pleasures, he fell asleep early, and so did his attendants. When he woke up early, the oil lamp was still burning. He saw his attendants sleeping: one with a lute in her armpit, another with a tabor on her neck, still another with a drum in her armpit; one with hair disheveled, another drooling, still another talking in her sleep. It was like a charnel ground before his very eyes. When he saw this, the misery became clear, and a feeling of repulsion stayed with him. He exclaimed a heartfelt utterance: “Oh the oppression! Oh the affliction!”
Yasa put on his golden shoes and went to the entrance door. Spirits opened the door, thinking, “No-one should create any obstacle for Yasa’s going forth into homelessness.” He went to the town gate, and again it was opened by spirits. He then went to the dear park at Isipatana.
Just then, after getting up early in the morning, the Buddha was walking up and down outside. When the Buddha saw Yasa coming, he came down from his walking-path and sat down on the prepared seat.
As he was getting close to the Buddha, Yasa exclaimed the same heartfelt utterance: “Oh the oppression! Oh the affliction!”
The Buddha said, “This, Yasa, isn’t oppressive, it isn’t afflictive. Come and sit down; I’ll give you a teaching.”
Thinking, “Apparently this isn’t oppressive, apparently it’s not afflictive!” excited and joyful, Yasa removed his shoes, approached the Buddha, bowed, and sat down.
The Buddha then gave Yasa a progressive teaching: talk on generosity, talk on morality, talk on heaven; and he revealed the danger, degradation, and defilement in worldly pleasures, and the benefit of renunciation. When the Buddha knew that Yasa’s mind was ready, supple, without hindrances, joyful, and confident, he revealed the teaching unique to the Buddhas: suffering, its origin, its end, and the path. Just as a clean and stainless cloth absorbs dye properly, so too, while he was sitting right there, Yasa experienced the stainless vision of the Truth: “Anything that has a beginning has an end.”
Soon afterwards Yasa’s mother went up to his stilt house. Not seeing him, she went to her husband and said, “I can’t find your son Yasa.” The merchant then dispatched horsemen in the four directions, and he himself went to the dear park at Isipatana. He saw the imprints of the golden shoes on the ground and he followed along.
When the Buddha saw the wealthy merchant coming, he thought, “Let me use my supernormal powers so that the merchant, when he sits down, doesn’t see Yasa seated next to him.” And he did just that.
The merchant approached the Buddha and said, “Sir, have you seen Yasa by any chance?”
“Please sit down, householder. Perhaps you’ll see Yasa seated next to you.”
When the merchant heard this, he was elated and joyful, and he bowed and sat down.
The Buddha then gave him a progressive teaching: talk on generosity, talk on morality, talk on heaven; and he revealed the danger, degradation, and defilement in worldly pleasures, and the benefit of renunciation. When the Buddha knew that his mind was ready, supple, without hindrances, joyful, and confident, he revealed the teaching unique to the Buddhas: suffering, its origin, its end, and the path. And just as a clean and stainless cloth absorbs dye properly, so too, while he was sitting right there, the merchant experienced the stainless vision of the Truth: “Anything that has a beginning has an end.”
He had seen the Truth, had reached, understood, and penetrated it; he had gone beyond doubt and uncertainty, had attained to confidence, and had become independent of others in the Teacher’s instruction. And he said to the Buddha, “Wonderful, Venerable Sir, wonderful! Just as one might set upright what had been overturned, or reveal what was hidden, or show the way to one who was lost, or bring a lamp into the darkness so that one with eyes might see what’s there—just so has the Buddha made the Teaching clear in many ways. I take refuge in the Buddha, the Teaching, and the Sangha of monks. Please accept me as a lay follower who has gone for refuge for life.” And he was the first person in the world to become a lay follower by means of the triple refuge.
While his father was given this teaching, Yasa reviewed what he had already seen and understood, and his mind was freed from the corruptions without grasping
Those are suttas and vinaya and the pali commentaries and sub commentaries said the same thing
Form Jhana is right concentration like how apple is fruit but to say that all fruits must be apple is far from the Truth
When some English commentators like us contradict earlier pali sub commentaries then we should give up our ego and let these later generation medieval arahants speak, we should prioritize their views over our views we are no pali scholar, we are no meditation master, we are no arahant and 1000 years after these medieval monks died we still weren’t born yet let alone knowing shit, let alone knowing how to interpret suttas and vinaya so pretending we know something when actually we know nothing won’t help our case it would increase our ego,selfishness and feeling that we are superior to these medieval monks that we know better than them so let’s give the job of interpretating suttas and vinaya and even pali commentaries to those who knows it well like earlier arahants ,2nd generation arahants, 10th generation arahants or monks who are no arahants but whose lineage or tradition could still be traced back to these arahants, we don’t know their teacher’s instructions better than they do, late commentators like us should not pretend that we know how to interpret pali commentaries let alone suttas, just give the job to earlier commentators who knows the context better, whose lineage could still be traced back to arahants,
the fact is the living meditation tradition stops at 10 ce so not even ajahn chah lineage could still be traced back to medieval arahants let alone ajahn brahm, ajahn thanissaro and others, without being disrespectful they are lovely, they should not stop teaching but we should not rely on them too much ,they are good but when they disagree with even earlier ajahns then we should know who to hear
And the earlier masters and ajahns said that form jhana is not necessary to attain enlightenment
If my English is better than now I could share more but English is a very difficult language, I hope google translate could be perfect in the future