The decision tree converters currently default to using the deprecated operator types, even in op versions where they've both been long-deprecated (didn't realize it was under the ml ops, not the regular ones). I believe the fix would be to use a default of op_type=None, plus if op_type is None: op_type = "TreeEnsemble" if op_version >= 5 else "TreeEnsemble...". There might be more that needs to happen for the node attributes, I haven't looked at the differences between the old op types and the new one too close.