Can’t speak to Berlin within the past 3 years, but I’ve never seen any sort of gate/turnstile entry to German train or subway. There are little punch machines in the stations most places, or just use that city’s transit app - Nuremberg’s is well-integrated with Apple Pay.
Enforcement is anywhere from routine and uniformed (IC/ICE), semi-routine (RE/RB/S-Bahns), to random and plainclothes (most subway systems).
Enforcement is anywhere from routine and uniformed (IC/ICE), semi-routine (RE/RB/S-Bahns), to random and plainclothes (most subway systems).