avrdude: Yikes! Invalid device signature. Double check connections and try again, or use -F to override this check.An error occurred while uploading the sketch
Expected signature for ATMEGA328P is 1E 95 0F Double check chip, or use -F to override this check.
Well, that is exactly what I selected!
I meant this was the selection throughout!
if I don't burn the bootloader of MightyCore, the TM1637 works perfectly and the UART is giving some random characters.