You are allowed to download your content onto a thumb drive and take it with you, but the university does not assist with the process after that point. You have never used another platform, and the university only provides support and instruction on its own platform.
The institution should ensure that students are able to maintain their ePortfolio beyond the constraints of the institutional platform, while providing instruction on how to transfer the content to a new platform. When students are using a platform where transfer is impossible, that should be explained initially, and another entity, such as a career center, should be available to help students create a public-facing resource. Alternatively, the institution can make the platform available to its graduates to continue creating portfolios.