Hi, I have same issue for update to 1.5.5 - 1.5.6
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://apt.hestiacp.com buster InRelease: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY A189E93654F0B0E5
W: Failed to fetch https://apt.hestiacp.com/dists/buster/InRelease The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY A189E93654F0B0E5
W: Some index files failed to download. They have been ignored, or old ones used instead.