Surya,
“What is beyond the witnessing consciousness is the subject of Vedanta: Brahman. However, it unnecessarily complicates life to even think beyond and nor does it help knowing. In Vedanta the prerequisite to its study if the mastery of Yoga itself.”
I don’t think much Vedanta is needed at all to simply understand that whatever becomes included as part of one’s knowledge becomes limited. If one says that one’s true nature is “awareness”, “consciousness”, a soul, a spirit, or even “emptiness”, “nothingness”, whatever can be said about it - one will be imposing limiting qualities onto it. If anything, it is useful to simply understand that the moment one starts clinging to any knowledge at all, one has created all sorts of barriers. If this is understood, even just on an intellectual level, that can be very helpful along the path.
“I think questions about what happens after reaching liberation are irrelevant. You are effectively asking what happens at the end of time, and ones mind cannot answer those questions.”
I agree. All too often, many spiritual traditions had become obsessed with the otherworldly at the expense of living this life. If one is not truly living, only then do such questions as to what happens after death of the body becomes relevant. Because life has somehow been found to be unsatisfying, one now needs all sorts of beliefs and philosophies to cover the void. It is mostly an effort to create some amount of security in life. The essential insights that had happened in the East is that there is nothing in existence which is not divine. If you see things with your own clear seeing eyes, beyond the prejudices and programming of the mind, there is nothing else except the divine. This is why amongst the Hindus, they have said that there are so many different “gods” and “godesses”, yet at the same time they have always said that everything is none other than a manifestation of Brahman. There is no other. If one truly understands this, then just very simple, ordinary things in life become divine. The ordinary is the beyond, and the beyond is the ordinary. The Buddhists expressed this in their own terminology - that “Samsara is Nirvana and Nirvana is Samara” - there is absolutely no difference between existence as it is and the so called “transcendental” reality.

Get to the HearT of things, deal with the root. otherwise, all is lost in the winds of mind.