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There have been a number of dark matter candidates put forward over the years, but we still don't seem to be much closer to finding an answer. This is where the d-star hexaquark - more formally, d*(2380) - enters the picture.

https://www.sciencealert.com/d-star-hexaquark-particles-could-be-responsible-for-creating-dark-matter

https://iopscience.iop.org/article/10.1088/1361-6471/ab67e8

I've seen similar claims for diquarks and pentaquarks so I would be hesitant on the DM claim.

I do not see how a hexaquark - or any multi-quark system for that matter - would fail to electromagnetically interact with its surroundings (i.e. absorb/emit light), which is a basic property of DM.