Wikipedia should never be considered a "source", even per its own documentation.

If you must, to support an assertion found in Wikipedia, follow the article's citations and use them. If they even do support the assertion. Quite often, they do not.

Source can have a broader meaning than just “primary source.”

It should not be considered even a "secondary source". It's by intention an aggregator of secondary sources. Which secondary sources are included or excluded, particularly for sensitive or contentious topics, entirely depend on the bias and endurance of the editors of the article, so what you'll get is a grab-bag. Wikipedia has no effective means of detecting and countering, for example, a professional team of coordinated editors, or motivated activists.

As a rule of thumb, think high-school term paper. If that's good enough for your purposes, then sure, use it as a "source".