Resolved! STM32U5xx: QSPI and SPI3 in DMA mode - callback comes too early - for you
I have my OCTOSPI1 as QSPI working - in "indirect mode", now using DMA: it generates a very clean waveform (no gaps between words or bytes as in "polling mode", a smooth waveform).I use also OCTOSPI1 as a "regular SPI transmitter" (acting as SPI Tx)....