Thanks @Daryl! Adjusting chunk-size when fitting a classifier has been recommended a few times on the forum for fixing this, e.g., MemoryError when Training Silva Classifier
I discourage using --p-feature-ext--n-features to solve the memory error, though. This will actually adjust how many features (kmers) are being considered when fitting the classifier, and hence could alter classifier performance. If you have memory constraints on your machine, chunk-size should be all you need.