Can I use Flutter to create a microsoft Excel task pane UI and if so how can I do it?

Question

I know you can create an Excel task pane UI with React and Angular, the Microsoft official docs explain how to. https://learn.microsoft.com/en-us/office/dev/add-ins/quickstarts/excel-quickstart-react.

I am trying to accomplish the same with Flutter.

I followed this Microsoft article for creating an Excel task pane ui WITHOUT using Flutter and it worked as expected and as explained in the article. https://learn.microsoft.com/en-us/office/dev/add-ins/quickstarts/excel-quickstart-jquery?tabs=yeomangenerator

I then created a web build of the sample Flutter counter app.

I copied the Flutter web build files to the src/taskpane folder that yeoman creates and simply changed the Flutter web index.html file name to taskpane.html, hoping this way I would not have to touch the manifest.xml file.

When I do 'npm start' Excel launches and I can open the taskpane and it seems to load, but the taskpane is blank, it does not show the Flutter counter app.