Recorded as
https://issues.apache.org/jira/browse/JENA-1900
The extra transformer plugin seems to fix the problem.
The problem is that there are several log4j2 "dat" files (in a manner
similar to ServiceLoader files loading META-INF/services) and shading
without modification will pick one, not combine them.
What is not clear is why the fulljar fails but the main server jar
works. This might be down to random order of combining the log4j2
plugin dat files keeping one that works for the limited use of log4j2 in
Fuseki by default.
Thank you Franco for the report - and the fix!
Andy