I'm talking about the System 7/8/9 days of macOS. I really like the aesthetic and workflow in the older macOS versions (call me a masochist) and I'm hoping if someone knows of something that already exists. I know there are plenty of skins/themes that hearken back to Windows 95/98, but most of what you find online when you look for "Linux like macOS 9" is things that make it look like modern macOS.
I found this post, but it refers to System 6: https://hexbear.net/post/786438
I did a quick search on r/unixporn (I just put in "System N") and found several posts, mostly about System 6 and System 9. Usually they post the links to the dotfiles in the comments. Good luck.
By the way, I don't think you'll find a specific distribution or desktop for what you want. You'll have to customize several things separately, look for documentation, dotfiles, etc.
Look into GNUstep and related projects maybe? I’m not sure how close it is to pre-NS Mac (that was OS X iirc?) but it might be close enough.