Decidim does not support
turbolinks so it is not included on our generated apps and it is removed for existing Rails applications which install the Decidim engine.
The main reason is we are injecting some scripts into the body for some individual pages and Turbolinks loads the scripts in parallel. For some libraries like leaflet it is very inconvenient because its plugins extend an existing global object.
The support of Turbolinks was dropped in d8c7d9f. If you are interested in bringing turbolinks back, further discussion is welcome.