Must also add -DDEBUG_ESP_PORT=Serial see other thread Debugging WiFiClient with an ESP8266 on PlatformIO - #3 by lbussy
Not good. Can you extend the buffer to like 4K by declaring static char readBuf[4 * 1024] = {0}; and tell us the output? Maybe there are some recognizable TLS headers or HTTP headers inside there, but that output looks undecodable to me oO
Is this dump maybe found in your binary at some other place? (On Linux you can do hexdump -C <bin file> to get the hexdump)