The cause is that there is a mismatch between location of native .so library and the code, which expects the library in a different location.

Reproducer:
# cat rep.java 
class rep { public static void main(String[] args) { org.fusesource.jansi.internal.JansiLoader.initialize(); } }
# /usr/lib/jvm/java-11-openjdk/bin/javac -cp /usr/lib/java/jansi/jansi.jar rep.java
# /usr/lib/jvm/java-11-openjdk/bin/java -cp /usr/lib/java/jansi/jansi.jar:. rep

Expected output: no output; exit code is 0
Actual output:
Exception in thread "main" java.lang.RuntimeException: Unable to load jansi native library
	at org.fusesource.jansi.internal.JansiLoader.initialize(JansiLoader.java:62)
	at rep.main(rep.java:3)
Caused by: java.lang.Exception: No native library found for os.name=Linux, os.arch=x86_64, paths=[/usr/java/packages/lib:/usr/lib64:/lib64:/lib:/usr/lib]
	at org.fusesource.jansi.internal.JansiLoader.loadJansiNativeLibrary(JansiLoader.java:338)
	at org.fusesource.jansi.internal.JansiLoader.initialize(JansiLoader.java:60)
	... 1 more

Intended code change: Fix the library location and/or the code that looks for library file

A new gating test is needed; the above reproducer should be turned into a test and made a mandatory gating test

No documentation changes are needed.

Actions to pre-verify the fix:
- make sure that a gating test was implemented, it looks sane, was ran and passed
- check whether other existing gating tests passed
- manually check whether package follows Java packaging guidelines wrt. JNI library installation: https://docs.fedoraproject.org/en-US/packaging-guidelines/Java/#JNI
  - JAR files using JNI or containing JNI shared objects themselves MUST be placed in %{_jnidir} and MAY be symlinked to %{_libdir}/%{name}.
  - JNI shared objects MUST be placed in %{_libdir}/%{name}
- check that running "mvn" in a terminal produces colorized output

Actions to verify the fix:
- check that running "mvn" (without arguments) in a terminal produces colorized output
- check whether all gating tests (existing and newly implemented) passed
- check whether Maven functional tests passed

Gating test was committed in https://gitlab.com/redhat/centos-stream/rpms/jansi/-/merge_requests/8
It failed as expected: http://artifacts.osci.redhat.com/testing-farm/7dbf12ff-3aca-4369-bc34-0a27dacb306b/

Commit:
https://gitlab.com/redhat/centos-stream/rpms/jansi/-/commit/931c4c2679b4448ebce73d905869a399552de5aa

Gating test was implemented, looks sane and passed.
The build follows Java packaging guidelines wrt. JNI library installation
Failed test: Running "mvn" does *not* produce colorized output.

I debugged this a little and found out that /usr/bin/mvn shell script sets "library.jansi.path property to ${MAVEN_HOME}/lib/jansi-native, which overrides jansi built-in library search paths.

The following merge requests address this issue:
https://gitlab.com/redhat/centos-stream/rpms/jansi/-/merge_requests/10
https://gitlab.com/redhat/centos-stream/rpms/maven/-/merge_requests/6

Tested jansi-2.3.3-5.el9 together with maven-3.6.3-13.el9
Running "mvn" produces colorized console output now.
The new build still follows Java packaging guidelines wrt. JNI library installation, except for libjansi.so file installation, which is installed into /usr/lib, not %{_libdir}, but this is fine per Java multilib exemption granted by FESCo https://pagure.io/fesco/issue/961
Still waiting for gating tests to pass.

All gating test for jansi-2.3.3-5.el9 and maven-3.6.3-13.el9 passed.
That makes this bug is pre-verified (sanity-only as no functional tests were ran).