Module not found: Can't resolve '@material-ui/core/Container'

Container is not part of the material-ui version specified in your package.json.

To upgrade, run the following:

$ yarn add @material-ui/core@next

You might have to remove the old stable version (if that's even an option for you).

React and react-dom >= 16.8.0 are all that are needed as peer dependencies, so the experimental upgrade of material-ui should be all you need to use Container.