Thank you for your reply. I think that we are interpreting that page slightly differently. The section that says:
WildFly 18 also is heavily tested and runs well on Java 8. We plan to continue to support Java 8 at least through WildFly 21, and probably beyond.
...reads to me as "if you want to continue using Java 8 on WildFly 18, then that's okay". But in the previous paragraph they write:
While we do want to run well on the most recent JDK, our recommendation is that you run WildFly on the most recent long-term support release, i.e. on JDK 11 for WildFly 18.
...which is saying "you can probably get away with JDK 13 but we recommend using an LTS release instead."
To me, the article you've linked seems to be quite unambiguously stating that JDK 11 is the preferred choice for WildFly 18.
Please could you take another look and see what you think.