Karma is a concept too. Someone called it a convenient fiction. That would make nonduality an inconvenient truth.
Shankara says begin at parabrahman. If it’s not being-existence-presence, consciousness-awareness-intelligence, holistic bliss infinity, it’s not parabrahman.
Nonduality is a concept too. It's like a convenient thorn used to remove the inconvenient thorn of our convenient fiction. Apres namarupa, la satcitananda!