You don’t write whether you’re using Musashi or Emu68, but the latter is already like a 68040.
With Musashi you can specify which cpu to emulate in the config file, with Emu68 you can not and it remains 68040-ish.
Where do you see that it says 68020?
As he mentions 020, he must be using musashi.
So as you said, he would need to edit the config file. I believe there are 2, one called amiga and default.
I have always used the default one. So maybe he is editing the wrong one.
Emu68k, is much easier. No messing around with linux install etc etc.