When setting up a new project and starting the app with--env.vueDevtools the Standalone Devtools open but cannot connect to the app.
Output in the console is the following:

 [VueDevtools] Connecting to http://localhost:8098... [VueDevtools] Failed to init: TypeError: doc.createElement is not a function

Downgrading and fixing the version of dev tools to6.5.1 fixes the issue. It looks like this is a problem with newer dev tools versions.