Arduino for STM32

Hi @stevestron and @stats2z,
I have found the solution thanks to your comments... it was so easy...
I am no experienced user of Arduino and I forget to write the wizard formula "while(!Serial) {};" in the Setup....
Once I did it everything started working properly.... in both Linux and Windows.
See ...

I don't get the last line of command dmesg..."cdc_acm 2-4.1:1.0: ttyACM0: USB ACM device"
... ie. USB port (/dev/ttyACM0) can't be then recognized by host PC

I normally use a bootloader for BluPill (generic_boot20_pc13.bin) to my full satisfaction.
But I also have a few HY-TinySTM103 boards in the drawer, into which I loaded the bootloader
intended for them (generic_boot20_hytiny.bin). Unfortunately, this bootloader doesn't work
at all and I can't figure ...