- Download the MacOS release .
- Install it.
- Download Java 17.
- Install it.
- Delete
/Applications/VASSAL 3.7.12.app/Contents/MacOS/jre
. - Move
/Library/Java/JavaVirtualMachines/temurin-17.jdk/Contents/Home
to/Applications/VASSAL 3.7.12.app/Contents/MacOS/jre
.