If my target university doesn't currently list a dMAT score requirement, should I still bother preparing seriously?

Yes, but only proportionately. Even where a university does not formally weigh the dMAT score in admissions, the certificate is still a required document inside your APS file, so if your degree field and intake are affected, you cannot skip taking the exam.

Why you still have to sit the exam

If your degree field and intake are affected, you cannot skip taking the dMAT even if the score itself carries no competitive weight at your specific target institution. The certificate is a required part of your APS documentation regardless of how the score is used.

How much preparation is enough

The practical approach is to prepare enough to clear the mean of 100 comfortably and move on, rather than over-investing weeks of prep time chasing a competitive score. Only two universities, RWTH Aachen's Battery Science track and Gottingen's Data Science MSc, currently use the score as a formal selection input.

My Advice

Prepare enough to clear the mean comfortably, then redirect your remaining energy to your SOP, LORs, and university shortlist; those carry demonstrated weight everywhere, while the dMAT score itself only matters competitively at two named programs right now.