Shadow 8.3.7 brings Gradle 9 support! Note: only Gradle 9 support is being backported to this version. No additional features or crucial bug fixes will be included in the 8.x line. Please migrate to Shadow 9 as soon as possible. https://github.com/GradleUp/shadow/releases/tag/8.3.7

Is there any ETA for when shadow 9 will leave the beta phase?

Now, or weeks later? There are some issues should be fixed before RC, I don't want any breaking change in the RC versions.