WhatsApp 2.21.18.17 (released on 15/09/2021) does not restore from local backup. We're trying to understand if it's just a temporary issue.

In order to fix this:

  1. perform migration as usual using older WhatsApp 2.18.248, then uninstall it
  2. when requested to update WhatsApp, install pre-2.21.10.16 WhatsApp release 2.21.9.15 downloading here or from APKMirror. This is because Play Store provides latest version only

Next WhatsApp updates will come automatically through Google Play Store.