head & tail report errors on boot and shutdown
This is a glibc/POSIX issue.
If you want to fix it, you can add
export _POSIX2_VERSION=199209
to the top of /etc/rc.d/rc.S

libwrap.so is missing so telnetd (amongst others)
doesn't work.

Don't expect gcc or anything in binutils to work.
They're Debian packages I converted to Slackware format
to see if I could use them.  I can't (but I didn't try hard,
and you'll be missing gcc-g++ too).

Some stuff like rdist (amongst others) require the gcc/g++
support library which is missing.

OpenSSL man pages are.. wrong.

fdisk, cfdisk, rdev are missing.

I can't think of anything else that might be broken, but
I'm sure there's lots.