But it makes a kind of sense, right? There's long been straightforward upgrade paths for 486 users, making the 486 effectively totally obsolete and killing most of the demand for continued support. Whereas 68k machines have effectively become trapped in time, and their users are still going to work to keep support going.

Is it still supported? The “News” page on the linked site reads:

Current Linux/m68k Releases

As of today, the following versions of the Linux/m68k kernel are "current":

Linux/m68k 2.0.36, released 5 February 1999, is a stable 2.0 series release. Users of earlier versions should probably upgrade; it's well worth it.

Linux/m68k 2.2.10, released 19 July 1999, is a developmental release (despite the 2.2 version number).

Linux/m68k 2.4.5, released 5 June 2001, is an experimental release. (More recent patches may be available in the linux-m68k mailing list archives.)

I would imagine there are actually more 68k devices out there than 486 and, I am told, the 68k architecture is much more enjoyable to work with.