The gwt-servlet-jakarta.jar is the one you want for using GWT-RPC in jakarta.servlet environments. Which classes that you need are not updated correctly?
The one (deliberate) omission I'm aware of is validation, but there is no server-side validation component for GWT. However, you may not be able to serialize validation types over gwt-rpc (though it is unlikely you were using this feature) though, since the built-in GWT implementation of validation is frozen at
1.0.0.GA - you'll need a different client implementation, and that implementation will need to be serializable over GWT-RPC to use in this way. See
https://gitlab.com/ManfredTremmel/gwt-bean-validators and
https://github.com/gwtproject/gwt/issues/9844.