Perhaps it's just me ...

[Jolipropre]

Thanks for your hints. I tried all this but could not get any data from the SDP610. This sensor seems to follow the I2C standard which is similar but not equal to the smbus protocol.
I found promising directions here:
https://developer.sensirion.com/index.php?id=589
but the story finally ended with a message that my gcc version is different from the version used for the kernel compilation.

Another procedure is described here
https://github.com/MLAB-project/pymlab
The install process took more than an hour and finished with an error message that I don't recall...
For now I have tried enough, I put aside these sensors now (all other sensors are perfect), maybe I come back to it when a later Raspbian release is available.