Hi @kafker ,
Thanks for reporting! We have not seen this error before, so it might be related to the very very recent release of GTDB 214 (just a few days ago; we have not had time to extensively test yet). We will investigate.
As a workaround for now, you can train a classifier with q2-feature-classifier instead (as shown in the previous step of that tutorial, so you have probably done this already).
Just out of curiosity, what kind of environment are you running this in? I see that you are running qiime2-2023.2 — but what other plugins or packages have you installed in that environment?