> it won't be long before someone comes up with a crazy chimera of an OS that can run DOS, Windows, Linux, BSD, and macOS binaries

TBF, the only missing part of this is that Darling isn't developed enough to run many Darwin programs; otherwise you can have that today by installing WINE+DOSBox+Darling on Linux or your pick of *BSD or illumos. (Well, running *BSD programs on other systems is a weak point, but otherwise.)