So Solved it like this.

As mentioned that with the upgrade of Spring boot 2.x to 3.0.X it failed. So we needed to use the classic JarLauncher the new package wasnt working. So upped the jar version to 3.3.X and with it added a mavern setting to use CLASSIC jarLauncher.

https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-3.2.0-RC1-Release-Notes

That made the springboot app to startup. but on the Spring-Ui page there was no operation listed saying "No operation found in spec!"

For that we tried multiple things with springboot 3.3.0 to 3.3.4 but didnt work. When upped the version to 3.3.5 it started to work.

Hopefully this helps some one.