Yes, this is about OneDrive's Windows Desktop client, but the All About sites cover mobile versions of Windows, such as on the excellent Surface Go range, plus many AAWP readers will be running various flavours of Windows, so this is definitely of interest. Microsoft has said that the OneDrive Desktop client for Windows 7 and 8.1 will stop working on 1st March 2022. This date may also be relevant for Windows 10 Mobile users, for whom OneDrive backups still work but which may also stop working on this date because of the roots of the mobile backup system in WP8.1. (Just my spidey-sense, though, I could be wrong.)

From Microsoft:

In order to focus resources on new technologies and operating systems, and to provide users with the most up-to-date and secure experience, beginning January 1, 2022, updates will no longer be provided for the OneDrive desktop application on your personal Windows 7, 8, and 8.1 devices. Personal OneDrive desktop applications running on these operating systems will stop syncing to the cloud on March 1, 2022. 

If you are currently using one of these operating systems, we recommend upgrading your operating system to either Windows 10 or Windows 11 to avoid disruption. For machines that do not meet system requirements for Windows 10 or Windows 11 operating system upgrade, you can back up and protect your files by manually uploading them to OneDrive on the web, and continue to access, edit, and share your files on all your devices.

Learn more: 

• OneDrive system requirements
• OneDrive desktop app for earlier versions of Windows
• Sync files with OneDrive in Windows
• OneDrive desktop app for Windows
• Move files off a Windows 7 PC with OneDrive
• Turn off, disable, or uninstall OneDrive

Of note is that if you still use Windows 7 or 8.1 then you'll still be able to manually upload (and download) things to (and from) OneDrive after this date, but you'll have to use a web browser and login that way, using the web interface.

The tie-ins with Windows 10 Mobile, its backup, and its OneDrive client are somewhat unclear, but I'll keep the relevant status page updated each month so that you know what still works and what doesn't, etc.