Difference between SonarQube 8.9.1 and 9.1 on rules

We would like to take into account the CFamily plugin (version in 6.20) in our configuration of SonarQube.
Currently in our company we are using version 8.1.0 of SonarQube and would like to upgrade to version 9.0.1 or 9.1 including report generation.
We would like to know the impacts in terms of rules (addition, deletion), metrics, or scritps command before moving to a more recent version in order to inform the projects in our company. How can I get this information?
Thank you so much.

Nota : I tried to create the topics and the categorie SonaSource Updates/releases but I could not

Hello @FredAubert,

For the CFamily related impacts, you have a look at the CFamily anouncements.
If you want an exhaustive granular list you have a look at the Jira project and filter by version. For example, this is from 6.21 to 6.27.