Thank you very much for the link and for the solution. I did not know the dependencies page.
However, I was misled by Xojo’s behavior.
The 2019 version opens, it makes me open the project regularly and, at compile time, it pulls me out 1440 errors of “Type mismatch error”, on classes and methods of other Plugins that had always worked.
While Xojo 2015 had given me, upon opening, a strange window where I remember (I’m 90% sure) literally “conflict” was mentioned.
I hope I will be able to try the plugin then. Thanks again.