Do non-creationist theories of the origin of the universe assume something came from nothing?

I’ll admit I’m not too knowledgeable in cosmology, but one common argument I hear for creationism is that the alternative assumes something came from nothing, which is less probable than something coming from something that always existed.

However, I’m wondering: do these theories necessarily assume something came from nothing? Is there anything inherently implausible about that? Are there are non-creationist theories of the origin of the universe that do not assume something came from nothing?

(Yes, I know I could “just Google it” but I’d like to hear from the intelligent crowd we have on this site).