JDK-8301119 introduced GB18030-2022 support. As a fallback, a property jdk.charset.GB18030 has been introduced to select the older 2000 standard. However, that no longer seems to be selectable with the Chinese locale and using the GB18030 encoding (which now defaults to 'gb18030-2022`).

This test:
$ cat Test.java
import java.nio.charset.Charset;
public class Test {
public static void main(String[] args) {
Charset.forName("GB18030");
if ("2000".equals(System.getProperty("jdk.charset.GB18030"))) {
Charset.forName("gb18030-2000");
} else {
Charset.forName("gb18030-2022");
}
}
}

Fails when run as such:

$ LANG=zh_CN.GB18030 ./build/linux-x86_64-server-release/images/jdk/bin/java -Djdk.charset.GB18030=2000 Test
Exception in thread "main" java.nio.charset.UnsupportedCharsetException: gb18030-2000
at java.base/java.nio.charset.Charset.forName(Charset.java:543)
at Test.main(Test.java:6)
$ echo $?
1