RESOLVED
A day or so after I wrote the original email, I reset the phone to the factory defaults, but Malwarebytes was still alerting me to the same malware. Then after a Malwarebytes update on June 19, the scan was clear and has remained clear.
I was not able to confirm this malware with Sophos (see first message) and did not install/try others.
ADVICE
I got no replies to my posting, which surprised me. BUT many of those posts that do get replies have used tags. So add tags - the more, the merrier. Good luck!