Maybe that I found something… thanks to a Github user:
https://github.com/Myzhar/Lepton3_Jetson/issues/2#issuecomment-693274740
Changing SPI mode from 3 to 1 at code level for the spidev driver the communication starts to work.
#define SPI_MODE_1 (0|SPI_SPHA)
...
#define SPI_MODE_3 (SPI_CPOL|SPI_SPHA)
I do not understand why this happens