Erel - thanks for moving me to the right forum and the format suggestions.
agraham - there was a missing class problem noted in the logs. (Most of my errors are programming sequence errors, so I forgot about the log!)
Then, I noticed I had forgotten to add:
#AdditionalJar: androidx.legacy:legacy-support-core-utils
Once I did this, my little test program worked fine, but the original program I was trying to update still did not. It must be something resulting from creating the test program in B4A ver 11 and the original program (for Android 4) in B4A from long ago (but still compiled using ver 11). So, I am cutting and pasting code from the old project into the new one and converting it to use ExternalStorage.
Thanks!
DougT