Re: error trying to save to database (Phoenix)

If you look at the dependencies of the 5.0.0-HBase-2.0 artifact https://mvnrepository.com/artifact/org.apache.phoenix/phoenix-spark/5.0.0-HBase-2.0 it was built against Spark 2.3.0, Scala 2.11.8 You may need to check with the Phoenix community if your setup with Spark 3.4.1 etc is supported by

Re: Looping through a series of telephone numbers

+1 to using a UDF. E.g., TransmogrifAI uses libphonenumber https://github.com/google/libphonenumber that normalizes

Re: [Building] Building with JDK11

Bytecode version is controlled by javac "-target" option for Java, and by scalac "-target:" for Scala JDK can cross-compile between known versions. Spark uses 1.8 as source and target by default controlled by the Maven property java.version