Booter for 9.3 kernel not working

Hi folks,

I have a Mac LC III that I was able to successfully install with
NetBSD 9.3.  The GENERICSBC kernel provided as part of the release
boots just fine, but no kernel that I have build, cross compiled or
native, has been recognized by the booting tool.  I found an old
thread https://mail-index.netbsd.org/netbsd-bugs/2015/11/17/msg043295.html
that suggested that -O2 may help, but that was ineffective.

My next steps were going to be to make 100% sure that I have the
latest Booter, and then to try to boot an older kernel to see if I can
make headway.  I was also going to try to see if I could get a native
boot option working
(https://github.com/schmonz/netbsd-mac68k-without-macos).  Am I
missing anything obvious?

Thanks,

Matt