User profile page by id?

[simon]

It would be great if there were a PUT endpoint for username . The use case is sites like mine which transitioned to SSO, to get all the usernames synced. Then my plan A would have just worked.

You can make a POST request to /admin/users/sync_sso for this. If you are using the Discourse API gem, you can use the gem’s sync_sso method for this. If you are not using the gem, see Sync SSO user data with the sync_sso route for details about setting up the request.