Hi Luca;
I checked DADA2Stats.qza in this code, and I find it is
173(0.48%) after I do the dada2...
And I change the primer to the universal primer used in dada2 handbook and loose the index, the reads rose to 232...
I check the link below to see the same problem happened to other people, but it wouldn't solve my problem.
high chimera rate in dada2 - User Support - QIIME 2 Forum