Depends; you should be able to still run binaries from the 90s, but if it's dynamically linked and doesn't ship with the libraries finding compatible libraries might be a pain and it won't run out the box. If you have the source code, then it should usually compile with minimal or no changes unless it depends on very old libraries that have seen incompatible changes (which is often the case). One of the nicer things about Windows is that it's a much more comprehensive "batteries included" system.

To put this in some perspective, I used Debian's debootstrap to install Debian Woody (2002 vintage) on a Linux 5 (I think?) kernel. It all worked as expected. I suspect the XWindows protocol is fairly backward, and you could recompile everything with the gcc Woody shipped. I guess that says a thing or two about Debian maintaining backward compatibility with older package formats too.

It's not a stunt I try to pull with Windows.

No, it won't compile. Not even kernel v4.8 can be compiled with gcc v11+.