Java version checking seems a little off. Global settings are set to default to Java 16, so trying to open a 1.12.2 pack without adjusting the settings shows the Java 8 warning, as expected, but after ...
So, if we backport the 2.13 fix to 2.12.8, we can make both Java 11 and alternative Java 8 compilers happy, but it will mean new versions of akka compiled with 2.12.8 would not be drop in compatible.