[Fixed]-TypeError: int() argument must be a string or a number, not 'Model Instance' – Heroku

Here’s the culprit:

profile = models.ForeignKey(Profile, default=Profile)
#                                    ^^^^^^^^^^^^^^^

You can’t set a Model class as a Foreignkey default. If you’re thinking of setting an hardcoded default then you should use an int and be sure the selected value exists as a key in your Profile model.