My understanding of the literature is largely that n-back training doesn’t generalize effectively, mostly just improving ones ability to perform n-back exercises.
Mine also. This article implied they did see generalization, at least to other working memory tests - but I can't find the full text to check what they used.
The only paper I’ve seen so far with any generalization used timing feedback to incentivize closer attention. Generalized Outcomes were believed to be due to improved executive function/attentiveness, not memory, which is what the time pressure aimed for.