As an agnostic, I have always been open to the idea of non-physical existence, and I see consciousness as one example of that. In my view, consciousness is non-physical or it is unlike any other physical thing in the Universe. I have argued that point-of-view for years. In this article, I will showcase some of my strongest points.

1. The ontology or nature of mental imagery
Mental images are visual representations of the physical world. Yet the mental imagery are lacking the usual properties we'd expect from physical things, such as being objectively observable, occupying space (e.g. hallucinations don't occupy space), having mass, etc. The one physical association we have is that they are connected to brain activity. Some use that to presume that the brain activity causes (as opposed to correlate with) mental images, which leads me to my point #2.

2. Would scientists ever discover subjective experience by studying brain activity alone?! (rhetorical)
Imagine that a scientist is living in a world where everyone is in a constant state of sleep. The scientist is then unable to communicate with any of the inhabitants. If the brain alone causes or leads to consciousness, then you'd expect the scientist to discover the subjective experiences of others by just studying their brains.

But from what we see in science so far, discovering consciousness by solely studying the brain has not led us to any verifiable explanation. In fact, to date the ONLY way scientists know about subjective experience is because we are able to report it to them. This is consistent with brain not being enough to explain consciousness.

3. Consciousness persists even in a limited or declining brain function (vegetative states and NDEs)
It was once thought that if a patient couldn't respond or follow commands that they were unconscious. We now know that that isn't the case given Dr. Adrian Owens evidence for patient's responding even while having 'locked-in syndrome'. So now we accept that consciousness can persists even during a vegetative state. Sure patient's in a vegetative state still have brain activity. But then there are cases where awareness is reported even at times where brain activity is slowed down (anesthesia) or even impaired and near-death, and yet some patients still report conscious experience. Despite there being brain activity in these cases, I still think they support the view that consciousness does not need brain because the type of brain activity during cardiac arrest and anesthesia should not leave consciousness intact (or at least not the ability for vivid experiences). People have to remember that it's not just any activity that scientists say leads to consciousness - as if even one neuron firing could salvage a conscious vivid experience, but rather you need a good amount of brain activity for vivid experience. If such vivid conscious experience can persist even during impaired brain conditions, then it's only reasonable to question if the brain is needed at all for consciousness, and if it's just that we can't measure awareness once the brain activity stops completely.

My Theory
My theory is that the brain is just a medium for consciousness. In other words, the relationship between consciousness and brain is that the two interact, but are not limited to each other. Consciousness can also exist without the brain and even as part of other mediums, like in Ai.