Thank you, now I understand. It had been removed AFAIK and replaced by a log file.
See:
https://forums.triplea-game.org/topic/2497/replace-console-logging-with-a-file
and
https://github.com/triplea-game/triplea/pull/8436
That doesn’t explain why it was present in 2.5 though. I vaguely remember that “Show Console” might have been an option in the Engine Preferences what had been removed later.