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Bit idea : The Witcher 3 written in assembly with 40 billion lines of code so you can run it on an old windows 98 desktop
(hexbear.net)
I don’t wanna any nerds in here explaining why this is impossible I choose to believe it could be done in theory
I was gonna write a thing about the feasibility but then I saw you say no so nevermind but here's a Minecraft classic clone on a 68k Macintosh https://youtu.be/5ZMkHnGCuhI
TLDW You don't even need to write something in assembly to port it to old hardware or operating systems! You just need a compiler (that turns your source code into binary instructions) that supports your target platform and any modern (compatible) source code should work. the video has good examples of the kinds of limitations you'll run into though.
I found a YouTube link in your comment. Here are links to the same video on alternative frontends that protect your privacy: