Microsoft has changed how users install apps and access cloud products. The my M365 portal, which was previously accessible by visiting http://portal.office.com, has been replaced by a new modal dialog within the Microsoft 365 Copilot app. Users will now be directed to https://m365.cloud.microsoft/.
Users will be able to download their apps by accessing the modal dialog in Apps > Install apps > Install Microsoft 365 apps in the Microsoft 365 Copilot web and desktop app.
This is related to broader changes at Microsoft relating to the new cloud.microsoft domain. This domain is specifically dedicated to Microsoft cloud products and is designed to provide a single and unified home for Microsoft 365 apps and services.As Microsoft services transition to cloud.microsoft, you may see your desktop and mobile apps, as well as your web browser, connecting to this domain. Redirects will help ensure that those still using older URLs end up in the right place. In most cases, you won't need to do anything to continue using Microsoft services the same way you used them on legacy domains.
For more information, see Download Microsoft 365 on a PC or Mac and Introducing cloud.microsoft: a unified domain for Microsoft 365 apps and services