Awesome! As an FYI, we use the "New plagiarism frammework" integration type for Turnitin so that submissions on the Canvas side are just file uploads. It works great with submit on behalf of as far as I ca tell. If you're using the L:TI version of Turnitin, submit on behalf of won't be an option. We had the LTI version before the new plagiarism framework was finalized, and honestly our faculty and students hated it as the experience for submitting, grading, and viewing feedback was so different from every other assignment, dates worked differently, etc... We were super happy when Instructure finalized the framework so we could switch over to that!
-Chris