Do meta keywords still matter for SEO?

No - Google ignores the meta keywords tag. Here is what actually matters:

• Meta keywords - Google stopped using the meta keywords tag as a ranking signal in 2009 and has confirmed publicly that it has no value for Google rankings.
• Meta description - different: it is used as the snippet under the page title in search results and influences click-through rate, but it is not a direct ranking factor either.
• An out-of-date adviser - small business owners told to “add meta keywords” by an SEO agency or website builder should treat that recommendation as a signal the advisor is out of date.

Spend the time on the meta description and the title tag instead - those are visible to actual humans and drive clicks.