I am having the same issue with the App router.

To support older browsers, we use both the App- and Pages router. The pages that need to be available for older browsers run smoothly in the Pages router. With this method, we can support browsers down to Chrome 49.

It is possible to remove the globalThis error (from the pages router) by using a global-this script, such as this one: https://github.com/ungap/global-this/blob/master/cjs/index.js