Using the ARDUINO USB 2 serial converter to program STM32?

Dear everybody,
I have used ARDUINO ETHERNET in the past, hence I had the ARDUINO USB 2 serial converter.

It is the previous version of this:

It has a Atmega8U2 programmed as a converter.

My intention is to use it as a converter to program a STM32F103C8T6 board:

Problem is I always get the following error message:

Failed to init device.
stm32flash Arduino_STM32_0.9
GitHub - rogerclarkmelbourne/Arduino_STM32: Arduino STM32. Hardware files to support STM32 boards, on Arduino IDE 1.8.x including LeafLabs Maple and other generic STM32F103 boards
Using Parser : Raw BINARY
Interface serial_posix: 115200 8E1
An error occurred while uploading the sketch

My system is a Macbook Pro.

Does any of you have experience with that?
Thanks!

did you activate the native bootloader with boot config pins?

hi there, do you mean the boot selector on STM32 board?

ccosmos:
hi there, do you mean the boot selector on STM32 board?

yes

Yes this was set to programming mode.
The issue is the Atmega8U2 of the adapter, I cant make it communicating with SMT32