Well, in principle, you have some virtual audio emulation in xrdp that plays audio (and with the neutrinolabs plugin supposedly is also able to record) in your debian VM. So, you should actually be running the opposite way - with playback to "Local" on your host, playing back the audio from your guest VM. You would not need any bhyve options for that, because you're not using any emulated audio hardware but the virtual RDP audio channel in the VM.
The
pactl
output tells me that pulseaudio seems to be fine in your host. If I were you, I'd try without the neutrinoplugin in debian, if that still fails to play.
I suppose, you did confirm before, that local playback (i.e. playing some music via VLC or a Youtube video in Firefox) in your FreeBSD host already works? So I'm assuming that, with the right remmina settings, this has got to work.
In the end, the setup should look something like this:
Code:
freebsd --remina/RDP------> xrdp | debian (bhyve)
audio playback:
local