So is there any information on how to get this game to use MT32 support properly in windows 10?

Which game?

I don't use Win 10, but if you prepare your own custom dosbox-version (I always use Taewoong's dosbox) of one of the older Ultimas, set "mididevice=MT32" and insert the two MT32-rom-files in the folder, I can't see a reason why it shouldn't work.

I did discover a work around... Coolsoft the makers of VirtualMidiSynth has a beta program they are working on called Coolsynth Midimapper (at least it was in Beta when I discovered this work around, I don't know what stage its on now)...

It is able to remap munt through to VirtualMidiSynth, and other program's built emulators. So I was able to get MT32 support working again (system wide).

http://coolsoft.altervista.org/en/forum/post/2120#post2120

It's slightly unstable perhaps, and crashed on me 'once' (causing the system to continually play a sound, and I had to log out of windows and log back in to fix it) but overall it works fairly well

It kind of reminds me how in windows 7 (and VISTA) you had to use Putzlowitch's to switch the midimapper channels around. But its likely working in a much different waythan Putzlowitsch did it... But the final outcome is basically the same for me as long as it does the job!

You don't have to use an external program to emulate Roland MT-32 in the (custom) dosbox. If you use the method I described, Munt and VirtualMidiSynth are not necessary. And it's absolutely stable in my experience. I've prepared all my dosgames this way and I like the thought of having a portable solution, as everything you'll need will be basically in one folder.

Ya, that'll work, you can also put mt-32 roms in scummvm folder too (as I understand it) and do the same thing (although I only ever got it to work if I copied the roms to each game folder directly for some reason).

Sometimes its helpful to do change output on a system wide basis for certain things. So its handy to discuss all options available.