The problem code is

static bool server_available(std::string_view host, std::string_view service) {
    // Resolve host name/service to IP address/port
    struct addrinfo * server_info;
    if (getaddrinfo(host.data(), service.data(), nullptr, &server_info) != 0) {
        return false;
    }
    
    // Create a socket
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        freeaddrinfo(server_info);
        return false;
    }
    
    // Attempt to connect to the server
    bool retval = true;
    struct timeval timeout;
    timeout.tv_sec = 1;
    timeout.tv_usec = 0;
    setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout));
    if (connect(sockfd, server_info->ai_addr, server_info->ai_addrlen) < 0) {
        retval = false;
    }

    close(sockfd);
    freeaddrinfo(server_info);
    return retval;
}

The problem is that when you test an IPv6 address you also need to create an IPv6 socket.  On systems where IPv6 is preferred, you almost always get an IPv6 address to test.

The AutomaticCommand::wait_for_network() seems pointless as you wouldn't get any addresses to test with if the network is down.  At least not when you get the addresses from DNS over the network.

Reproducible: Always