Arduino for STM32

Hello,
I do not understand what really happens in Setup() function on a WeAct Blackpill F411 V3.1.

When I write Serial.println("setup complete") at the end of my setup, I cannot see it if I don't do put a delay(1000); before.
Why do I have to put a so long delay()?

I also use a SSD1306 display ...

Ok, I successfully uploaded my sketch with a STLink V2 dongle.
Thanks a lot.

Regards,
Alain

Hum well ok, I'm going to try with STLink dongle...
I'll let you know.
Thanks.

Thanks but I already did that.
I Wonder if I still have a bootloader...

Hello,
Thanks but unfortunately, that doesn't work...

Hello,
I already uploaded a sketch to my Blackpill F411 v3.0 board few months ago with Arduino 2 and it continues to execute this sketch.
Anyway, I now want to update it and I cannot do it anymore.
Maybe, setting has changed, don't really know, I 've read many posts about such kind of problem but ...