MOTU 828mkII FW and OS Mojave

Hi everybody,
I’m the owner of an old MOTU 828mkII FW and I think it’s still a good soundcard for what I need but recently I have problems trying to set MIDI-audio preferences in my mac mini late 2012; in particular: I had set MOTU analog outputs 5-6 for audio filepreview or internet audio streaming as they go to a couple of Creative computers monitors while I have main outputs going to my ADAM A5X but now I can’t no more find out a way to change this setting…
I checked on MOTU swebsite and I have latest firmware and drivers installed so I can’t understand; do you think it could be my MOTU is no more compatible with OS mojave? I didn’t find anything about it…
Thanx,
arfo