I wanted to know if any ClassNotFoundException or similar unexpected exception is raised when one applies the CVE-2021-44228 aka Log4Shell hotfix as recommended here.

Result: It looks like no exception is bubbling up.

To test this execute the following commands:

./gradlew clean installDist
env JAVA_OPTS=-Xmx64M ./build/install/log4shell-hotfix-side-effect/bin/log4shell-hotfix-side-effect

It will log a bunch of messages and timings and there should be no exceptions.

If the log4j jar file is not patched properly there should be a measurable delay between the messages (or you might even get an RCE, YMMV).