@kionite231 from what I hear if you try to use an unofficial APK, then from that point onwards WhatsApp will refuse to run on anything but stock unrooted Android. Not quite a blanket ban like you're looking for, but if you use #LineageOS or something it would render WhatsApp unusable.
Unfortunately my guess is the error message will also be something that blames the user (like "please use a standard Android from an authorised distributor") which would defeat the purpose for you