That's not correct. They can claim what I posted above, which is true. The energy always existed.
"Did a Supreme Being create this matter?"
No. It always existed.
"If a Supreme Being did not create this matter, how then did it come into being?"
The energy always existed. Any change observed is due to natural forces. There's no way to distinguish scientifically, anything other than that.
"It is unknown if atheism is true or if creationism is true"
Both are false. It is impossible to prove a negative, which atheism is. They are simply relying on Occam's razor, the KISS principle which says anything invented beyond the simplest explanation is irrelevant and meaningless. The word creationism means belief in a Biblically literal creation. The term was coined ~1875. That is false on physical evidence.
The difference between what Occam's razor eliminates as irrelevant and meaningless, and Christianty, is that the person of God showed up and told us who He is and explained Himself. That is observable evidence. There is no other religion where the diety showed up in person. That includes the real possibility, that the appearence of this universe and all in it was His doing. That is His claim and He pointed out the dual. The dual is that one can't uncover from physical science, the presence of a prime mover. The cause for "creation" can not be distinguished simply by looking at the physical world.
One either believes what Jesus said, or they don't. It's that simple. All a Christian can say, is that they believe what He said. All an atheist can claim, is that they don't believe him, Occam's razor applies, and it is the same meaningless, irrelevant story equal in real value to all the other stories.