Apt update reporting signature cannot be verified

Hi,

whenver I am running apt update I am seeing thsi error:

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://apt.radxa.com/bionic bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B99C4BEFEC47E96E
W: Failed to fetch http://apt.radxa.com/bionic/dists/bionic/InRelease  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B99C4BEFEC47E96E
W: Some index files failed to download. They have been ignored, or old ones used instead.

Does anyone know how this can be fixed ?

Hello. Try adding the public key to the apt keyring.

wget -O - apt.radxa.com/bionic/public.key | sudo apt-key add -

Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead

Now in 2024 and on different distros, warning still persists.

No matter how many different posts and guides I followed, various distro names but doesn’t get a clean result.

Latest command tried:
wget -O - apt.radxa.com/bullseye-stable/public.key | sudo apt-key add -

Still getting “Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead”

Is there a better way to configure?

On the package page itself are directions on how to enable it:
https://radxa-repo.github.io/bullseye/

# Install signing keyring
keyring="$(mktemp)"
version="$(curl -L https://github.com/radxa-pkg/radxa-archive-keyring/releases/latest/download/VERSION)"
curl -L --output "$keyring" "https://github.com/radxa-pkg/radxa-archive-keyring/releases/latest/download/radxa-archive-keyring_${version}_all.deb"
sudo dpkg -i "$keyring"
rm -f "$keyring"