Our solutions come with a preconfigured certificate. You need to substitute those certificates with valid ones.
As @rob83 mentioned, the file you downloaded is not X.Y.Z, that's a placeholder, you need to substitute that placeholder to extract the files (the latest version is 3.3.0 now)
curl -Ls https://api.github.com/repos/xenolf/lego/releases/latest | grep browser_download_url | grep linux_amd64 | cut -d '"' -f 4 | wget -i -
tar xf lego_v3.3.0_linux_amd64.tar.gz
sudo mkdir -p /opt/bitnami/letsencrypt
sudo mv lego /opt/bitnami/letsencrypt/lego
Then proceed with the commands in the guide