I followed the nice tutorial here:
https://community.openhab.org/t/migrating-dsl-rules-to-jsr223-javascript-with-a-case-example/73352
to create my first rule. I saw that the lewie libraries had supposedly been superseded by the ones here:
so I tried those first (putting them in the correct, different, directory) but I couldn’t get anything to work. So I reverted to the lewie libraries and my “Hello Openhab” rule worked.