IBDesignable and Inspectable button

when I installed the additional components
Which additional components precisely ?

IBInspectable shows the error: "Overriding non-open property outside of its defining module" 
Where exactly ? Is it a message in IB ? Or in code ? If so, could you show the code and the exact place where error occurs ?

I understand that is an existing code that you open in Xcode 12.2. Exact ?
Did you get the error with previous versions of Xcode ?
Did you update code as proposed in Issue navigator ?