There is no such thing as a "native" Pages application because it is not bundled with the operating system. The last compatible version of Pages for Big Sur 11.7.* is Pages v12.1, clearly not the v14.1 presently in the Mac App Store that requires macOS Ventura 13.* or later for installation.
No version of Pages v5.* is compatible with macOS Big Sur 11.* and has not been available since macOS 10.11.
If you ever personally installed Pages from the Mac App Store since Oct 2013, then you can get the latest compatible version for Big Sur installed from the Mac App Store — provided you use the same Apple ID. You would launch the Mac App Store, sign-in with that original Apple ID, and then press cmd+0 (zero) to open the Purchased panel. If Pages appears there with a download or install symbol, click that. You may receive one or more dialogs, none of which would you click Cancel. The final dialog will ask if you want to install the last compatible version of Pages for Big Sur and you know what to do at that prompt.