Hi @Sausage_Mahoney, thanks @thermokarst and @ezke.
Reducing the --p-chunk-size (from 262144) may help, but we've never had problems with classify-sklearn running out of memory before.
How much memory does your machine have?
If you're willing to share SPN_S3_R1_R2.join.filteredseqs.qza I would be happy to debug.