I was thinking the same before launching our product.
To me it is interesting that PH doesn´t offer the DM option. That means, you have to reach out to other co-founders on other platforms.
Engage with people’s posts/comments, and if you find someone interesting, have a look on their profile. Most people have their LinkedIn and Twitter profiles there.
Why are you looking for a co-founder btw? Just curious☺️
EraseID