@ahahlberg   I have a temporary fix - I used my wife's Pixel 5 phone to set up the KASA account and then was able to do a straight login on my Samsung phone.  So it's definitely a compatibility problem with the Samsung Galaxy S8+ environment and the "Create Account" function of the KASA app.

ahahlberg wrote

I have a Kasa Smart Wi-Fi Light switch with the dimmer function model HS220(US).

On my Samsung Galaxy S8+ phone when I try to create an account in the Kasa app by selecting "Create Account" button I briefly see the usual e-mail and password and confirm password screens which is immediately replaced with a screen showing the two checkmark items you have to select to confirm the account and my phone's keyboard app.  I cannot scroll the screen to get back to the e-mail and password fields and I cannot see them to confirm the entries.

Can anyone explain to my how to get around this glaring flaw in TP-Link's KASA App? 

I've installed hundreds of apps via Google Play on this phone, including the Cync and Smart Life apps I have for other IOT lights and switches, and never had a problem like this.  But this KASA app must never have been tested on a Samsung Galaxy S8 phone like all the hundreds of other apps I have.

So here I sit with a brand new IOT dimmer switch and I'm unable to use it because of this KASA app's unique flaws.

So before I send this back, is there another app that will work with this switch?  Or is there some alternate way to create a Kasa app account for this device?