You missed one - V2_OS . A full OS written in assembler. Un-en-shittification at its finest! I ran it very early in its life, got it to boot, then couldn't do

You missed one - V2_OS . A full OS written in assembler. Un-en-shittification at its finest! I ran it very early in its life, got it to boot, then couldn't do much else with it :) ... and you may consider DESQview . Not quite an OS, but a precursor to Windows.