Comment # 2 on bug 1209438 from Sarah Kriesch

I have fixed the "invalid indicator" issue. You need additional line numbers
without the "--free". Therefore you have to use that with only -x:
000100 IDENTIFICATION DIVISION.
000200     PROGRAM-ID. HELLO-WORLD.
000300 PROCEDURE DIVISION.
000400     DISPLAY 'Hello world!'.
000500     STOP RUN.


But you will receive the same error message then:
/tmp/cob3910_0.c:11:10: schwerwiegender Fehler: libcob.h: Datei oder
Verzeichnis nicht gefunden
   11 | #include <libcob.h>
      |          ^~~~~~~~~~
Kompilierung beendet.