Hey there.
We don’t any any specific document to share enumerating those plugins, but the details are mentioned in the upgrade notes.
Upgrade simplified: Languages, Git and SVN, LDAP/GitHub/SAML support now built-in (8.0, 8.5)
All plugins related to languages, Git/SVN support, and LDAP/GitHub/SAML authentication are now built into SonarQube itself. If you were using these plugins, you need to remove them from your extensions/plugins directory before upgrading. Read more in this community guide: SonarQube v8.5 and Beyond: Where did all the plugins go?
Did you add any additional plugins to your v8.1 installation that didn’t come preinstalled (you can always download a fresh v8.1 zip to compare). If not, there’s no further action you need to take.