snd_hda not useable if loaded via /boot/loader.conf
When loading snd_hda from /boot/loader.conf it is loaded, but cannot be used and configured. At least audio/moc does not work, it is unable to use the OSS interface. But after unloading and loading snd_hda again the sound card is useable.
As a workaround I added "/sbin/kldload snd_hda" to /etc/rc.local and then the soundcard is useable form audio/moc as OSS device.
snd_hda was the only sound kernel module that has been loaded via /boot/loader.conf.
Kernel configuration is GENERIC x86_64 (v18.104.22.168.gec4cf).