If you are interested to download the database 21c, it’s available for download now on Oracle Software Delivery Cloud.
Mike Dietrich has written a step-by-step post to navigate in E-delivery and download the software.
If you are interested to download from Oracle’s portal, it’s shown there as well. Check the blog post.
So start the download as I am going to do myself and in next post, we shall see the installation of it.
Hope that helps.