It will be quite straight froward to evaluate desktop users' behaviour by using card sorting session.
Shall I stick with card sort?
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It all depends of your specific objectives.
Card sorting is ok to have a view on users' representations of groups and labels (for mobile, desktop, or even print or service design).
But "finding content" is not only about categorization, it also deals about guidance, discovery and learning strategies, readability...
Therefore, user-testings could also be interesting, with a wide spread of methodologies (with or without verbalization, synchronous or asynchronous, eye-tracking, with or without a scenario to follow...). You may also consider interviews or focus groups.
So, it all depends of what you're exactly looking for. Maybe you should sharpen your question.