You can "upload" via SFTP (instead of HTTPS) by leveraging the upgrade API:

https://www.odoo.com/documentation/13.0/webservices/upgrade.html

Hi,

If you don't want to upload the database to the Odoo upgrade(​​https://upgrade.odoo.com/database/upload), you have to do the database migration yourself. But the tools are limited. If you need to migrate the database by yourself, you can check the option such as open upgrade project and talend tool.

If you are not interested to upload the database thinking about the privacy of the data, see the odoo privacy policy: https://www.odoo.com/gdpr

Thanks