@BG
Brian,
I've found that the documentation for v3 mentions Java 8, but has some very outdated links to recommendations for builds. For Mango versions 4 and 5, we recommend using Azul Zulu, so in this case I would recommend Azul Zulu JDK 8, which you can find here (I filled in the Java version, OS, and architecture for you): https://www.azul.com/downloads/?version=java-8-lts&os=rhel&architecture=x86-64-bit&package=jdk#zulu
I would recommend installing via RPM, instead of dropping a ZIP somewhere. Then, remove Java 21 to reduce confusion and the possibility that Mango still picks up 21.
Also, a heads up. We don't test with or support MariaDB, so I'm unsure if you could run into issues there. If it was working just fine for you before, then I'm sure it'll continue to work, but just letting you know.
Liv
Radix IoT