I think that the properties of antimatter are pretty well established to be identical to that of matter. For instance, the light spectrum of antihydrogen is known to be exactly the same as ordinary hydrogen. I don't think many (any?) researchers are looking at antimatter as an option for dark matter.

(Also, I always thought of antimatter as an abstract thing that gets made in the lab and that was cool ... But we use it for practical things every day. For instance, PET scanners in medicine produce positrons and watch the annihilations inside your body. Astoundingly cool to me.)

Good point! I forgot about PET scans.

The problem with antimatter is that it very much interacts with normal matter, quite violently in fact. So if dark matter was antimatter we’d be bathed in a sea of radiation as it continually annihilated with ordinary matter, which would make it quite easy to detect ;)