Currently the API of slf4j is used in deegree. See what slf4j is offering on options:

List of logging APIs (incomplete):

• Apache Log4J 2: https://logging.apache.org/log4j/2.x/
• Apache Commons Logging (JCL): https://commons.apache.org/proper/commons-logging/
• SLF4J: http://www.slf4j.org/
• Logback: http://logback.qos.ch/
• Tinylog/Tinylog 2: https://tinylog.org/
• java.util.logging (JUL): https://docs.oracle.com/en/java/javase/11/docs/api/java.logging/java/util/logging/package-summary.html

Adding a chapter to the documentation how to swap the logging framework and how to build a WAR using an individual Maven POM shall be added.

Log4j 1.2 has been reloaded into https://reload4j.qos.ch/ which provides an updated version of the old log4j 1.2 API.

The TMC has the notion to move from Apache Log4j2 Version 2.x to logback as the default logging provider for the deegree 3.5 line.
The handbook shall include a short description how to replace logback with the prefered logging framework by users.