[snovymgodym]

I mean you can grab SIMH and trivially have a working PDP11 emulator on pretty much any system that has a C compiler.

Then just get 2.11 BSD (or V7 Unix if you're a minimalist/masochist), install it, and you're free to write/run/debug all the PDP11 assembly you want.

But I do question the value of doing this. I'm a big believer in the notion that you can't train skills by proxy, so if your goal is to become proficient in writing assembly for modern architectures, then you might as well do so by learning a modern architecture.