Logging in with Apple ID still not working in iOS 12.5.6 on iPhone 6

This issue has been previously reported on 12.5.5.

When logging into Apple ID and iCloud with the Settings app, I get the message, "Software Update Required: Update this iPhone to the latest version iOS to sign in". Checking under Settings>General>Software Update reports "Your software is up to date". I tried logging out of my Apple ID, but get this error when trying to log in.

I can log into the App Store, and doing so shows my Apple ID in the settings app. However, I still see 2 "Apple ID Suggestions" below my Apple ID in Settings. One reports "iPhone Not Backed Up", and the other "Update Apple ID Settings: Some account services require you to sign in again". Following with prompt results in the error above.