The critical difference between Buddhism and Advaita Vedanta;
In Buddhism, the term
anattā refers to the doctrine of "non-self" – that no unchanging, permanent self or essence can be found in any phenomenon.[note 1]
While often interpreted as a doctrine denying the existence of a self,
anatman is more accurately described as a strategy to attain non-attachment by recognizing everything as impermanent, while staying silent on the ultimate existence of an unchanging essence.[1][2][3]
In contrast, Hinduism asserts the existence of Atman as pure awareness or witness-consciousness,[4][5][6][note 2] "reify[ing] consciousness as an eternal self."
https://en.wikipedia.org/wiki/Anatt%C4%81
While some claimed the Buddha remained silent on the existence of ultimate existence [thing-in-itself], a deep dive into the Buddhist texts will reveal the Buddha denied and refuted the idea of atman as it leads to endless cycles of rebirth and sufferings.
Kant on the other hand was very explicit in his CPR that the thing-in-itself is illusory but nevertheless a necessary and useful illusion.
While the Buddha rejected the ideal of the thing-in-itself as illusory, the Buddha did not condemn but allow lay-Buddhists to lean on idols, deities and gods, based on the idea that such are useful illusions related to their state of spiritual psychology.
Realization;
When a fetus is enclosed in embryonic fluid, it is already
realizing within
its level of cognition of the reality of what is supposedly 'water'.
This is the realization process prior to perceiving, knowing and describing what is supposedly 'water' in an adult person.
In an adult the realization power and process so its state of realization is more developed than that of the fetus.
The fetus realization power and process of its state of realization is more developed than its ancestors as evolved from that of the bacteria; this is prior to the adult perceiving, know and describe that realization.
As such, when an adult person perceives, knows and described 'water is H20' the prior processes of realization as already embedded in the body, brain and mind cannot be denied.
There is no mind-independent liquid [as the p-realists claimed due to ignorance] because the liquid labelled as 'what is water' is already entangled with humans prior to birth and inherited from 3.5 billion years of conditioning.
There are many types of realism re reality.
General the term realism and realist refer to philosophical realists who claim reality is mind-independent.
Rigoristically, an anti-realist in one perspective maybe a realist in another perspective and vice-versa.
As such, when using the term 'realism' one must be very familiar with the contexts involved.
Kant did claim he was an ANTI-Realist in one sense but also a realist in another sense.