UNITE version 9.0 is out, and I've built classifiers for it compatible with the newest version of Qiime2:
Older versions are still available here: Releases · colinbrislawn/unite-train · GitHub
Eventually, this will be superseded and UNITE provided directly on the data resources page, after RESCRIPt PR #134 is merged.
Need a different database? Send me a direct message!