The public CUDA GPG key does not appear to be installed

I am following this guide to install Cuda 11.7 on Ubuntu 20.04 via WSL2.

  1. CUDA Support for WSL 2
    Option 1: Installation of Linux x86 CUDA Toolkit using WSL-Ubuntu Package – Recommended
    4.sudo dpkg -i cuda-repo-wsl-ubuntu-11-7-local_11.7.0-1_amd64.deb

throws an error,
Preparing to unpack cuda-repo-wsl-ubuntu-11-7-local_11.7.0-1_amd64.deb …
Unpacking cuda-repo-wsl-ubuntu-11-7-local (11.7.0-1) over (11.7.0-1) …
Setting up cuda-repo-wsl-ubuntu-11-7-local (11.7.0-1) …

The public CUDA GPG key does not appear to be installed.

To install the key, run this command:
sudo cp /var/cuda-repo-wsl-ubuntu-11-7-local/cuda-B81839D3-keyring.gpg /usr/share/keyrings/

so when I try to run the above command, nothing happens.

I have read the similar thread, however, the solution offered by [mattshilling] does not work for me.

I have also tried removing the old signing key and installing the new cuda-keyring package with these commands:

$ sudo apt-key del 7fa2af80
$ wget https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/x86_64/cuda-keyring_1.0-1_all.deb
$ sudo dpkg -i cuda-keyring_1.0-1_all.deb

from this thread, Updating the CUDA Linux GPG Repository Key | NVIDIA Technical Blog

so I dont know how to go past this error. please help?