The SAmkhya KArikA ( as per the most ancient MAthor Vritti) is Niriswara VAdi. That means it does not accept the existence of a sole creator Iswara. It actually neither accepts nor rejects.
But, according some others, SAmkhya is Saiswara VAdi too. So, I think this depends on the interpretations which may vary.
But the philosophy does talk about a creation. Here, the conscious Purusha is the efficient cause (Nimitta KArana) and the inert Prakriti is the material cause (UpAdAna KArana) for the creation.
And, from their union, like that between a lame and a blind, the whole creation comes to existence.
Purushasya darsanartham kaivalyArtham tatha pradhAnasya |
pangandhavadubhayorapi samyogastatkritah sargah ||
For the Kaivalya (or liberation) of the Purusha and for the Darshana
(or Bhoga or enjoyment) of the Prakriti, from the union of the Purusha
and the Prakriti, like that between the lame (which is Purusha) and
the blind (which is Prakriti), the whole creation (sargah) comes into
SAmkhya KArikA 21
And,as already said before, NO, the text explicitly does not say anything on whether God exists or not.
Their philosophy, is entirely woven around the 24 Tattvas (25 if we include Purusha) and no talks about a sole creator whatsoever.
I have the book MimAngsA ParibhAshA. And, i have gone through it cursorily. Like SAmkhya, it too does not explicitly reject the existence of a creator. It does not talk about it actually.
NOTE: SAmkhya KArikA is based on Kapila's teachings only just like MimAngsA ParibhAshA is based on Jaimini's teachings.