He explains it in the original paper¹ & says in no uncertain terms that he believes the brain is a machine & minds are implementable on machines. What he is actually arguing is that substrate independent digital computation will never be a sufficient explanation for conscious experience. He says that brains are proof that consciousness is physical & mechanical but not digital. Searle is not against the computationalist hypothesis of minds, he admits that there is nothing special about minds in terms of physical processes but he doesn't reduce everything to substrate independent digital computation & conclude that minds are just software running on brains. There are a bunch of subtle distinctions that people miss when they try to refute Searle's argument.

¹https://home.csulb.edu/~cwallis/382/readings/482/searle.mind...

Quick definitional help for anyone who clicks on your link: the term "intentionality" in this context has a specialized meaning. In reference to mental states, it's the property of being about something, as in, "Alice is thinking about Bob." It doesn't necessarily have anything to do with intent, per se.

https://plato.stanford.edu/entries/consciousness-intentional...