If I have a PhD in computer science, could I contribute to philosophical outlets or would I need a philosophy PhD to do that?
You don't need even one doctorate to contribute to any field. Publications accept or reject papers based on the papers not the &quot;qualifications&quot; of the authors.
Just write your papers and submit them. Of course you might also work to develop some collaborative relationships with philosophers who can also give you advice on things.
And at any large (and some small) universities, you can just wander over to the philosophy department, find their coffee lounge, and start up a conversation.
Doing actual research in philosophy, however, probably requires a somewhat different skill set than in CS, but you can develop that.
And don't confuse Opinion with Philosophy. In any field, you need a basis for what you write for it to be publishable.