About migrating Outlook add-ins from old Outlook to new Outlook

Question

There is information that the following new Outlook will be migrated from 2024.

https://www.microsoft.com/en-us/microsoft-365/outlook/outlook-for-windows

Due to the new Outlook starting next year, we are verifying the operation of the Outlook add-in in order to migrate from the old Outlook to the new Outlook.

After loading Office.js, the value of Office.context.ui becomes undefined after the Office.onReady (which means Office.js is ready to use) event handler fires.

This worked fine in the old Outlook, but when testing the operation in the new Outlook, it seems that an error occurs because there is no value for Office.context.ui.

The process of starting the add-in and the error flow is as follows.

Create a new email > Start the Outlook add-in in the new email dialog > Outlook browser starts > Access the web application > An error occurred when referring to the method of Office.context.ui (the value of Office.context.ui is for undefined)

I would like to know if there is a specific solution on how to obtain Office.context.ui.