So there is a lot, in the interest of brevity, that I did not include in my original post.
I know that Flow does not officially support OneDrive. I probably should not have included that in my original post, sorry for the confusion.
I am moving the files from Dropbox to Teams, which stores the files in Sharepoint. I am NOT wanting to do this for user Dropbox Folders, just a Dropbox Shared folder for one large department with an extensive folder structure.
As I said in my original post, this will be a slow rollout of 3-5 users at a time, due to organizational needs, in a department with 60 geographically dispersed users. I am not doing a hard cutover where all the users will transition on the same day. I will have users from the department using either Dropbox or Teams/Sharepoint for the storage until the whole department is transitioned over.
I am aware of the Sharepoint Migration tool. I have done a lot of work with it previously, including scripting mass migrations Powershell to hand to the migration tool. I would prefer not to use that tool for this migration because it is a one direction update.