IPMI SOL seems to not accept characters after getty starts

tl;dr pxeboot new x86 host, ipmi sol works in loader, not after multiuser.

The FreeBSD cluster just acquired 4x Supermicro X11DDW-L and I am having
the hardest time with the IPMI SOL interface.

I have configured "COM2" as the IPMI SOL interface and enabled console
redirection.  Netbooting via pxeboot works well and the loader menu is
interactive and responds.

After NFS booting into freebsd (current or stable/11), getty fires up
and attaches to ttyu0.  It prompts me correctly, but it does not accept
my keystrokes.

If I do not configure /etc/ttys to enable a tty unconditionally (on vs
onifconsole), I see dmesg/kernel boot messages but never get a tty.

Its as though FreeBSD does *not* recognize the IPMI SOL port as the
console or something and I'm super confused.  Any thoughts here?

sean