AFAIK the initial prototype called nogil was developed by a person named Sam Gross who also wrote a detailed article [0] about it.
He also had a meeting with Python core. Notes from this meeting [1] by Łukasz Langa provide more high-level overview, so I think that they are a good starting point.
He also had a meeting with Python core. Notes from this meeting [1] by Łukasz Langa provide more high-level overview, so I think that they are a good starting point.
[0] https://docs.google.com/document/u/0/d/18CXhDb1ygxg-YXNBJNzf...
[1] https://lukasz.langa.pl/5d044f91-49c1-4170-aed1-62b6763e6ad0...