Booting a 660AV?

I've got a 68k-based Mac which is missing most of its case plastic, but
the sticker on the bottom identifies it as an M9040, which based on
what I've manged to find says it's a Centris/Quadra 660AV.

Naturally, I'd like to run NetBSD on it.  But I'm having issues even
before I really get started.

In particular, the mac68k pages make it look as though the only known
way to boot them is to boot into MacOS and then run a Booter program.
But this machine's keyboard is ADB and video is a DA-15.  I doubt I
have any of the latter and I'm not sure about the former.

Is this a lost cause for me?  Or is enough publicly known about the
660AV ROM boot procedures that all I need (heh) is to find enough
documentation and I can boot it from the bare metal?

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