Just before I left on this trip, there was an announcement from the German government that they would be beefing up border security and checking passports on all land arrivals.

I've entered Germany 3 times by train, from Denmark, Austria and Czechia. Not once was my passport checked. In fact the only time it was requested (except for hotel check-in) was in Syracuse (Sicily), where police were checking all arrivals by train. My passport was at the bottom of my bag and I took so long digging it out that the police got bored and waved me on.

I definitely strongly recommend carrying your passport everywhere if you visit Europe, but it seems the security measures were more chest thumping than anything else.