Absolutely, definitely, categorically — perhaps.
The real question is whether every mathematically possible universe including many based on different laws of physics can produce a universe that contains beings and entities even remotely resembling those found in Cthulhu Mythos.
Certainly there are specific aspects of the Mythos which are patently and scientifically absurd. For example, bat-wing alien beings capable of flitting across interstellar space. Now this doesn't prevent the existence of beings capable of self-propelled interstellar motion, but it is highly probable they don't come equipped with bat-wings. This doesn't obviate a version(s) of the Cthulhu Mythos existing according to physical laws in their specific universe.
Just considering one of the possible ramifications of string theory which suggests there 10500 possible configurations of physical laws. Yes that is ten raised to the power of 500, and this implies an unimaginably range of physically possible types of universes. Once you consider all the possible arrangements of matter and energy even within each type of universe, then it is possible that just taking into the existence of Cthulhu Mythos like features appearing in any of these universes that it is conceptually possible.
Conceptually possible means precisely that. Namely, that we can conceive of the concept as possible, but have no idea of whether it might exist or not in reality. Besides, with the Cthulhu Mythos like features these could range from one or two that vaguely similar to full scale cosmologies that are absolutely chock-a-block filled with Cthulhu Mythos creatures and civilizations.
The only reasonable answer is, and remains, perhaps. However, anyone engaged in their own worldbuilding project can fudge the possibilities and make it absolutely certain.