The error message "unknown key type ed25519" typically indicates that the version of the SSH client or software you're using does not recognize or support the ED25519 algorithm. ED25519 is a more modern public-key algorithm that offers better security with faster performance compared to RSA, but it's only supported in more recent versions of SSH clients and software. Here's how you can address this issue:

1. Update Your SSH Client

To resolve the issue, you may need to update your SSH client to a newer version that supports ED25519 keys. The process to update your SSH client depends on your operating system:

• On Linux: Use your package manager to update the openssh package. For example, on Ubuntu or Debian-based systems, you can use:
  sudo apt-get update && sudo apt-get install openssh-client
• On macOS: macOS usually keeps the SSH client up to date with system updates. However, if you're running an older version of macOS, you might need to update your system to the latest version. Alternatively, you can use Homebrew to install a newer version of OpenSSH:
  brew install openssh
• On Windows: If you're using Git Bash or another terminal emulator that includes an SSH client, make sure you're using the latest version of the software. For Windows 10 and later, the built-in OpenSSH client can be enabled and updated through the "Optional Features" settings.

2. Use an Alternative Key Type

If updating your SSH client is not an option, or you still encounter issues after the update, you can generate a key using a different algorithm that your current client supports, such as RSA. When generating an RSA key, it's recommended to use a key size of at least 4096 bits for better security: Remember to add the newly generated key to your SSH agent and to your GitHub account:

3. Verify SSH Client Support

After updating, you can verify that your SSH client supports ED25519 by checking its version or by listing supported key algorithms: Or for the list of supported algorithms: Look for ssh-ed25519 in the output to confirm support.

Final Steps

Once you have resolved the "unknown key type ed25519" issue by either updating your SSH client or using an alternative key type, you should be able to successfully clone the repository without encountering the original error. If you generated a new SSH key, don't forget to add it to your GitHub account to ensure smooth access to your repositories.