Since your comment is flagged to death, I'll leave this here for a more hands on approach for interested people:

https://interlisp.org/ is one of the systems which ran on these machines at the time.

Due to the stars aligning right in a syzygy it is now available as open-source, updated to run on modern systems. Even in a browser, without installing it.

Another one would be https://cuis.st/ which is the nearest Smalltalk-80 like thing available. Not as toyish as Squeak, not as bloated as Pharo.

Or even more 'original': https://github.com/rochus-keller/Smalltalk