dear Patrick:
You begin with:
"At the start of the Universe there is nothing, nothing exists, not even time. The most fundamental notion, a state of existence itself, has to be defined. But as nothing exists, how can a state of existence be defined ? The only solution is simply to introduce a state of non-existence."
I should like to tarnslate this as ;
An emergent phenomenon is a universe on itself that for a specific agent inside may be infinite wihout a beginning or an ending. This emergent phenomenon (illusion/reality) from the "outside" is not existing, so without beginning or ending, no start. Time and Space are also emergent phenomenae inside the first one. so is existence, because existence needs time and space. The non existance means that it is a state outside existence and therefore existing...
Your UB is an existing entity in an emergent phenomenon, where its non existence of it is an effect of its existence. Indeed without consciousness the yes or no inside this emergent ohenomenon would be zero, data without consciousness is chaos.
About the "primordial existence of consciousness I invite you to read/comment and give a RATING to my essay "The Puropse of Life"
I gave you a high rating becaus you really are touching the essence of REALITY, only in my point of view you have to take a step further.
Best Regards
Wilhelmus de Wilde