I thank you for the exhaustive details.
The replacement of the LNB is due to the fact that it is very old (almost 15 years, bought to use on HB13) and the cost is quite affordable to try to gain a few dB.
Then in the future (at the end of housework ... David!) I decided to commit to receiving HVS from a receiver that would certainly perform better than the current one.
Have a nice day !!