My memory of 1990s Linux development is hazy (I was a young kid at the time), but my recollection is ~5 years after this post they paid a huge cost in effort to get it to work on Alpha, and after that the required effort to port to other stuff went down. So maybe it's more like "simple initial implementation, massive rewrite later".
Edit: Also worth noting that the 386 was the first "modern" Intel CPU in terms of instruction set and interfaces provided to kernel developers, so requiring 32-bit CPU with an MMU excludes a lot of machines in 1991 but not so many machines in the years that followed. What he's saying is he won't port to 286 which is a very obvious decision but maybe not so much if your frame of reference was Minix.
(Later on I do seem to remember there used to be a port of Linux to MMU-less varieties of 68K in the late 90s, like some of the other replies are asking for. Not sure how well it ever worked.)
Edit: Also worth noting that the 386 was the first "modern" Intel CPU in terms of instruction set and interfaces provided to kernel developers, so requiring 32-bit CPU with an MMU excludes a lot of machines in 1991 but not so many machines in the years that followed. What he's saying is he won't port to 286 which is a very obvious decision but maybe not so much if your frame of reference was Minix.
(Later on I do seem to remember there used to be a port of Linux to MMU-less varieties of 68K in the late 90s, like some of the other replies are asking for. Not sure how well it ever worked.)