I've filed https://github.com/wildfly/wildfly/pull/17049 which, if merged, will change what developers need to do to run the testsuite against WildFly Preview.

Instead of -Dts.ee9 you would use -Dts.preview.

For bootable jar testing instead of -Dts.bootable.ee9 you would use -Dts.bootable.preview.

I configured the ci.wildfly.org jobs that test main to use both sets of properties, so they can test the PR. Once it's merged I'll remove the ee9 variants from the job configs.