Can you quote your sources, where does it say that?
I recently ran an EJB application on Java 11 no problems. Maybe they're referring to the fact that some modules were removed from the standard library, and that you have to declare an explicit dependency on them if you want to use them.
EJB support is not and never was part of "Java". EJB is defined by the Java Enterprise Edition spec, which is a completely different document than the base Java spec, and in fact, the JEE spec has been turned over to the Apache Jakarta group and is no longer owned by Oracle.
The JEE spec defines many more things than just EJB. It's also where the spec definitions for servlets/JSPs and JavaServer Faces. And much more. It's highly unlikely to go away anytime soon.
Aside from that, as of the EJB3 edition of the spec (JEE 6), a subset of EJB is defined that can run on reduced-stack servers like Tomcat and Jetty. It's the Java Persistence Architecture, and can not only be used in minimalist servers, but in places completely outside of the webapp server environment. I've used it to write offline (batch) database maintenance utility apps.
With such a large user base, not only can it be expected that EJB will remain an active part of Enterprise Java computing, but if Oracle did attempt to do something that broke EJB - or any other part of JEE - that there would be a loud howling from the user community.
Blitzlügen - Lies or information broadcast, but when called out the broadcaster does little or nothing is done to correct them, thus allowing those who wish to believe to accept them as truth.
Lügensturm - A barrage of Blitzlügen fired in such quick succession that it is essentially impossible to correct them all.