That's a great question. I think the only thing you can do is address who your competition is, even if they're only tangentially related. I usually follow a pattern of "X competitor is doing Y, which helps our target customer solve A and B need but not C and D".
I think it's worth finding the closest competitor no matter how far away they are, even just to signal that you've done the research.
I think it's better to mention the tangential ones than to omit them because it shows that you've really thought through the competitive landscape.
Competition is also not a bad thing. If there are a few startups vying for attention in a certain space, it means there's obviously value there. You have to prove to investors and customers that you're going to do it better and ultimately win the lion share of the space.
I think it's worth finding the closest competitor no matter how far away they are, even just to signal that you've done the research.