1. When I run STS4 under Fedora's (definitely a JDK) JDK 11, it does not detect it as such and shows

   The JRE you are running Eclipse with appears to not be a JDK.

   Spring Boot Live Hovers will not work with a plain JRE.

   

2. This happens whether the STS4 platform bundle is used, or using it as a plugin in either Fedora's Eclipse packaging or eclipse.org's Eclipse.

3. On Fedora 32/33 if I set -vm to Azul or AdoptOpenJDK 11 it is indeed detected correctly and STS4 runs normally.

Some questions:

1. What technical means does STS4 use to detect if the JRE is a JDK?
2. Any ideas why a JDK is not detected as such? BTW I have definitely installed the java-11-openjdk-devel package, and Eclipse runs non-STS4 projects fine.

From this screenshot though, are live hovers actually working?