You cannot use version 2.20.xx or higher. You need the final Gingerbread-compatible builds. Search for:
: Sites like Uptodown and APKMirror maintain archives of older APK files.
Whether you’re reviving a vintage Samsung Galaxy Y or trying to bypass the "This version of WhatsApp became out of date" error on an older tablet, finding a functional version of WhatsApp for Android 2.3.6 (Gingerbread) is a common challenge.