No registered import/export controller for entity type "taxonomy_term"

The first problem I encountered was that content_as_config_content_as_config_controllers() was, reasonably, looking for a controller called TaaxonomyTermController. In fact, it's TaxonomiesController. Once I fixed that, I found that ContentAsConfigCommands::getController() was passing the value of $this->controllerInfo[$entity_type] to instanceof, which expects a variable rather than a string. Once I created a class instance from that string and threw in an empty() check just to be safe, drush exports ran nicely. (This proved true both for my own case, taxonomy terms, and for #3207282: Drush command missing controller for "block_content" entity type's of block_content.)