What are default user account and password of Fedora 31 Cloud Base Image for OpenStack?

The OpenStack article Get images, has this information:

The simplest way to obtain a virtual machine image that works with OpenStack is to download one that someone else has already created. Most of the images contain the cloud-init package to support the SSH key pair and user data injection. Because many of the images disable SSH password authentication by default, boot the image with an injected key pair. You can SSH into the instance with the private key and default login account. See Configure access and security for instances for more information on how to create and inject key pairs with OpenStack.

It also says:

Note

In a Fedora cloud image, the login account is fedora.

I would try user fedora and password fedora, but if this doesn't work, some images are created so that password login is not possible, and you will need to follow the above link for using a keypair to login.