Competition wants to collaborate. Now what?

A few days ago, I posted about my startup on a relevant subreddit (post here) and let things sit for a few hours.

Shortly after, I started receiving DMs from another redditor, who claimed they had been working on the same problem for 10+ years that my products are actively solving. With my hackles up, I started doing some digging. Here's what I learned:

• This person appears to be pretty genuine. As in, they make wholesome, thoughtful comments on niche/geeky subreddits…not exactly the ones I'd subscribe to, but I feel a kinship with regardless (being a different sort of geek)
• The one book they had published was legit, though I found the reading experience to be clunky at best (I come from a publishing background and spent a lot of time crafting the experience in my books)
• It appears that this person hasn't yet figured out an effective and repeatable process to produce blended language books at scale, but he has "worked out the logic to the process of translating books." I'm not really sure how those two things are distinct; this person doesn't appear to have developer chops of any kind (I thought I knew what logic was. And then I started coding 😅😩)
• This person claims they have a well-connected and well-funded developer friend who is working on similar-ish problems, and he is hoping that they can work together
• This person has a background in marketing from a major US metro area

I'm holding my cards pretty close right now. Are there recommendations y'all have for keeping an open mind, but protecting yourselves at the same time?