We know in Bön a few Dzogchen lineages:
Zhang Zhung Nyen Gyud
They were teached by Buddha Tönpa Shenrab Miwoche.
All in all is Bön herewith rich on Dzogchen lineages with a very old 18.000 years tradition.
Must say that all Dzogchen does not stem from Tibet.
Nyingma Dzogchen sytems from India and was spread by Garab Dorje or Prahevajra
Bon Dzogchen stems from Ta zhig and finally form Iran.
Bon Dzogchen like the ZZNG is written in the native old Zhang Zhung language whereas Nyingma Dzogchen is written in Sanskrit. This means that ZZNG is older then the Nyungma Dzogchen form India.
Prahevajra was born not long after the Paranirvana from the Buddha Shakyamuni.
That would mean that Nyingma Dzogchen was not teached by the Buddha Shakyamuni.
Best wishes with your personal practice