[Uciaucrx]

Does anyone have info on discussions on concentration in the Nikayas?

welcome Michael

imo, it is important to distinguish between Right Concentration (Samma Samadhi) and wrong concentration

Right Concentration is supported by seven factors of the Noble Eightfold Path

this Right Concentration has its foundation is letting go of attachment & craving per the instruction in the Noble Truths

for example, Bhikkhu Buddhadasa was a scholar monk that made such a distinction

with metta

Element

The Blessed One said: "Now what, monks, is noble right concentration with its supports & requisite conditions? Any singleness of mind equipped with these seven factors — right view, right resolve, right speech, right action, right livelihood, right effort & right mindfulness — is called noble right concentration with its supports & requisite conditions.

Maha-cattarisaka Sutta: The Great Forty
And what is the faculty of concentration? There is the case where a monk, a disciple of the noble ones, making it his object to let go (vossaga), attains concentration, attains singleness of mind.

SN 48.9 & 10
And this, monks, is the noble truth of the cessation of stress: the remainderless fading & cessation, renunciation, relinquishment, release & letting go (vossaga) of that very craving.

Setting the Wheel of Dhamma in Motion
As for samadhi, an empty mind is the supreme samadhi, the supremely focused firmness of mind. The straining and striving sort of samadhi isn't the real thing and the samadhi which aims at anything other than non-clinging to the five khandas is micchasamadhi (wrong or perverted samadhi). You should be aware that there is both micchasamadhi and sammasamadhi (right or correct samadhi). Only the mind that is empty of grasping at and clinging to 'I' and 'mine' can have the true and perfect stability of sammasamadhi. One who has an empty mind has correct samadhi.

Heart-wood from the Bo Tree: Ajaan Buddhadasa