Non Dwijas aren't qualified to acquire knowledge of Brahman from Vedas(Upanishads) but can acquire so from Itihasas and Puranas. Are there any meditational techniques prescribed in them to realize Brahman for Non Dwijas? Can Brahman be realised without the 32 Upasanas in Upanishads? If yes what are those meditational techniques in Itihasas and Puranas prescribed to realize Brahman? How did Vidura etc all attain Bramha Jnana and Yajnavalkya also says learn Bramha Jnana from Sudras in Mahabharata. Reading Astavarka Gita Avathuta Gita Bhagavadgita Ribhu Gita etc all bestows knowledge of Brahman and prescribes meditational techniques? Note : I am aware of Varna system which can change also but please don't give me that answer. Kindly answer from traditional way.
There are many books other than upanishads that talk about meditation techniques for realising Nirguna Brahman.
For example, Atma bodha
Sitting alone freeing the mind from desires and controlling the senses, meditate with unswerving attention on the Atman.
The wise one should intelligently merge the entire world-of-objects in the Atman alone and constantly think of the Self.
He who has realized the Supreme, discards all his identification with the objects of names and forms. He is as an embodiment of the Infinite Consciousness and Bliss. He is the Self.
More descriptions can be found in earlier verses
Through discriminative self-analysis and logical thinking, one should separate the Atman from the sheaths..Consciousness (Atman) does not shine in everything though all-pervasive. Only if there is inner equipment (Buddhi/manas), He is manifest just as the reflection in a clean mirror...
Similarly, In avaduta gita
The essence and the whole message of Vedanta is this Knowledge, this supreme Knowledge: that I am by nature the formless, all-pervasive Self.‖ Meditate on this Truth to realise the Self.
- The firm experience of the nature of the Self is seen to proceed from inquiry
Similarly, Bhagavad Gita with Shankara's bhasya etc., yoga vasistha etc. provide many details on self-enquiry.