Anyone running linux on a 486 today, probably isn't using it as a desktop, it's probably a bare bones headless setup being used as some kind of embedded controller for some industrial process. Even into the late 90's 486 SBCs (Small Board Computers) usually about 5x8 inch in size were quite popular for embedded applications and likely there are still many out in the wild quietly controlling whatever process they control. This is the kind of shit that if it ain't broke you don't touch it cause it will probably be big $$$ to get something modern and certified put in it's place.