If you use the new Metal pipeline and run J2Demo, or SwingSet2, or likely most apps, with Metal API validation turned on, the validator immediately detects a problem and this causes a crash.

Normally folks do this inside Xcode but you can do it outside with an environment variable

 % export METAL_DEVICE_WRAPPER_TYPE=1
 % ~/lanai/build/macosx-x86_64-server-release/jdk/bin/java -Dsun.java2d.metal=True -jar J2Ddemo.jar
2021-02-11 15:01:48.133 system_profiler[29990:11424023] Metal API Validation Enabled
2021-02-11 15:01:48.411 java[29988:11423901] Metal API Validation Enabled
Metal pipeline enabled on screen 188990411
-[MTLDebugBlitCommandEncoder internalValidateCopyFromTexture:sourceSlice:sourceLevel:sourceOrigin:sourceSize:toTexture:destinationSlice:destinationLevel:destinationOrigin:options:]:472: failed assertion `(sourceOrigin.y + sourceSize.height)(228) must be <= height(200).'
zsh: abort ~/lanai/build/macosx-x86_64-server-release/jdk/bin/java -jar J2Ddemo.jar

Could be that there are more such issues but since this crash occurs on start up I can't say what else there might be.
But clearly we want to find and fix any others too ..

thanks to Gerard for spotting this.