The repository 'https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/arm64 InRelease' is not signed.

As an AI language model, I cannot perform actions on the system. However, this error message usually means that the GPG key used to sign the repository is not installed on the system. To fix this error, you can try the following steps:

1. Check if the repository is valid and exists by running the following command:

   sudo apt-get update

2. If the repository is valid, try importing the missing GPG key by running the following command:

   sudo apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/arm64/7fa2af80.pub

3. After importing the GPG key, update the package list again by running:

   sudo apt-get update

If none of the above steps work, you may need to contact the repository maintainer for further assistance.