I've been there too. Installing, trying, running older and older Unixes in SIMH. 4.1BSD, 32V, V7, V6, all the way down to V0 on the PDP-7.
I still keep a neatly organized folder of primitive Unix systems with their RK drive images and SIMH boot scripts.
But going all the way back to the Big Bang at V0, a funny thing happened.
The essence wasn't still there, things were still missing, because indeed the open-source foundation wasn't only born from Unix and the PDP-11.
No. The missing half of the puzzle is ITS and the PDP-10.
This is where GNU and the free software philosophy was born. The root of emacs, LISP, TeX, and many more. And interestingly, they're both older and more timeless than the Unix part of the puzzle. Unix (and then Linux) just happened to be a hardware abstraction layer for what really mattered. And then I reached the end of my journey to enlightenment.
I finally understood that GNU's Not Unix!
GUIX as the OS it's the ultimate GNU system witht he spirit of ITS+Emacs.
Not everything open and insecure, but hackable up to the last bit.
You can even run Guix System with the Hurd kernel. It really feels like a forgotten dream renewed.
I have a strange nostalgia for the old Unix days that I was too young— perhaps not even alive yet— to experience the first time around. It's what draws me to learning and using things like vim, Perl, awk, sed, etc. Those tools feel arcane and mystical.