E: Failed to fetch http://mirrors.aliyun.com/ubuntu/dists/focal/multiverse/binary-arm64/Packages 404 Not Found [IP: 119.167.250.242 80]

This error message indicates that the package manager was unable to fetch a package from the specified URL because it could not be found on the server. Specifically, the URL http://mirrors.aliyun.com/ubuntu/dists/focal/multiverse/binary-arm64/Packages returned a 404 Not Found error code, indicating that the file or resource requested does not exist on the server.

Possible causes of this error could include:

- The package was removed or renamed on the server.
- The repository URL was mistyped or outdated.
- There was a temporary issue with the server or network connection.

To resolve this error, you could try the following steps:

- Check the URL to make sure it is correct and up to date.
- Verify that the package is still available in the repository.
- Try refreshing the package list or updating the package manager to see if the issue resolves itself.
- If the issue persists, try changing to a different repository or contacting the repository maintainer for assistance.