Here is a list:

• python apps and cli with brython (this should be spawned in some sort of worker or iframe so that you can choose what is exposed to the instance)
• (node)js cli with eval() (this should be spawned in some sort of worker or iframe so that you can choose what is exposed to the instance)
• make the Microsoft store download apps from some sort of registry (so that the community can make apps)
• put a widget in the store which allows the user to create a webview app (the user enters a URL and it installs an app for that website using an iframe
• use Microsoft Oauth2 for login and use Microsoft to store the file system of the user or use the local storage API
• allow apps to create cli

Here are some apps already available as webpages:

• WhatsApp
• mail (Outlook)
• Netflix
• discord