My mom has a Huawei phone (we are in Asia), the model where the power button is the fingerprint scanner, I set up my fingerprint as a test, works surprisingly well, a little iffy when setting up since the button is so narrow unlike a full circular front or back scanner. That's from a one time test and not daily usage though, normally she doesn't lock her phone 😀
I think the power button on an iPad would be intuitive as well, because your index finger is reaching for that anyway, and you can setup your the thumb on your other hand for the times when you pick up the iPad upside down, as in left hand thumb, right hand index finger... but what about when it's picked up horizontally?? I suppose that would mean four fingerprint IDs for maximum convenience 👍👉👎👈. That sounds inconvenient, but it's more troublesome to always spin the iPad around for your index finger or thumb. My mom does need a new iPad one of these days, hers is really really old (and slow), but she isn't going to lock it anyways, so fingerprint whatever.