Then I got to your second paragraph. Yes. You're on the right track. Buddhism and Hinduism are "designed" not only to demonstrate the "true reality" beyond appearances, but to show that the end of suffering lies in that direction.
It is true that mindfulness as it is commonly understood may not lead to what you seek. The primary obstacle you'll face is that mindfulness is typically dualistic -- there's a _you_ observing a _that_. If the true nature of existence does not distinguish subject and object -- that is, if it is nondual -- then this will always be a stumbling block.
I eagerly recommend to you two similar paths. One is Advaita Vedanta. Examples of sages and teachers would be Ramana Maharshi, Nisargadatta Maharaj, and more recently, Greg Goode and Rupert Spira. Check out Goode's "Standing as Awareness" for the most clearheaded investigation I've found.
The other path is the pinnacle of Tibetan Buddhism: Mahamudra or Dzogchen. You can find a Mahamudra manual online at chagchen.com. It was authorized by one of the great living masters of the tradition, so it's legit.
In both cases, having a teacher to keep you from wandering off into nonsense may be critical. Check out "the Advaita trap" on YouTube for a somewhat humorous example of that.
As you investigate Buddhism more deeply, never forget that the different schools have more philosophical differences than commonalities, despite the kumbaya face they present. The mystical traditions of Hinduism and Buddhism are far more similar to each other than to their parent traditions, and folks from neither school will openly admit this. And if you continue to follow the Theravada tradition, make sure you understand the difference between being an arhat, bodhisattva, or Buddha. If you're into "seeing through the illusion," this will be important.