Instead of chasing a dead "WhatsApp XAP download link," turn your Lumia into:
Once you download the file (e.g., WhatsApp_2.18.200.xap), verify its size. Legitimate final versions are roughly 45–55 MB. If it is 2 MB, it is malware or a stub.
Before you search for a "WhatsApp XAP download link," you must understand the file format.
If you own a Windows Phone 10 device, you would actually look for an .APPX or .APPXBUNDLE file. However, most search queries for "WhatsApp XAP" target older devices like the Lumia 520, 635, or 930 running Windows Phone 8.1.
Microsoft and WhatsApp had a close partnership in the early 2010s. The official download source was the Windows Phone Store (later rebranded Microsoft Store).
When WhatsApp announced the end of support, Microsoft delisted the app from the store. There is no official "WhatsApp XAP download link" hosted by Meta (Facebook) or Microsoft anymore. Trying to download WhatsApp from the Store on your device will result in an error: "This app is no longer available."
This has forced users to seek third-party archives.