there isn't a Dzogchen master alive who would say that Longchenpa's writings are anything other than the purest expression of the the Dzogchen view we have. So, I will ignore the snide aspersions being cast upon him here.
he says, in the tshig don mdzod (chapter 2)
These impure phenomena of cyclic existence don't waver even the slightest bit towards something other than being emergent from within rigpa's range, enduring within its range, and remaining as mere playfulness within its range, just as dreams don't waver from sleep's range. Showing them to be empty forms in actuality, mere miraculous displays which clearly manifest while non-existent, reveals the thorough purity of cyclic existence.
from the Garland of Precious Pearl Tantra:
Your speech and actions in their own nature
are the conduct of radiant and empty rigpa;
the flow of your conceptual reifications, whether positive or negative,
are the vast space of contemplation's stream.
Your abberant views and/or valid claims
are the impartial view of natural attunement ("yoga")
All your clinging hopes and fears
Is the fruit of being completely unimpeded.
kun byed gyal po, 7:
There is nothing that is not perfect.
One is perfect, two is perfect, everything is perfect.
All actions are easy because they are already accomplished and perfect.
"One is perfect" signifies perfection in pure and total consciousness.
"Two is perfect" signifies perfection in the manifestations of consciousness.
"Everything is perfect" signifies perfection in completeness.
Thanks to this teaching on the perfection of the one,
you can enter in the state of enlightenment.
Thanks to the meaning of perfection in duality,
you can understand that everything that appears
is the perfect manifestation of consciousness.
Thoroughly tame your own mind.
This is (possibly) the teaching of Buddha.
"I must finally conclude that this proposition, I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind."
- Descartes, 2nd Meditation 25