No, I doubt that is something anyone could know for sure. We can narrow it down, though. I know, for example, that Albion shows MT-32 as a music option, and it is a 1995 game. There are probably more recent games than that. Moby Games can help, but it mixes in re-releases in its search results, so it's hard to know without clicking into each game to verify original release date.

Pretty likely it would have been in 1992. PQ1VGA and Laura Bow 2 were 2 of the last Sierra games to have MT-32 composed scores (probably the last two). King's Quest 6 kinda sorta had some tracks optimized for the MT-32 but it is a bit nebulous as to how much. The score was composed for General MIDI.

By 1992 most games were adopting the Roland Sound Canvas (General MIDI) as 'the standard'. Various games will have a MT-32 driver but very few will have any proper MT-32 support (some have none whatsoever but retain an installer option!). In the case of Sierra games, some backwards compatibility was given to the early GM games (1992 mostly- eg KQ6, GK1, QFG3) but from about 1993 onwards the support was mostly zero (e.g. LSL6, KQ7).

Thanks

Some releases of X-Com had CM-32L (LAPC, actually) music with no option for GM although the GOG release has both.

So we're all using slightly different terminology. OP asked "last game made for mt-32" in subject line, and "last game that used mt-32" in the body.
I answered from a "last game that supported mt-32" point of view while Spikey answered from a "last game that was composed for mt-32" point of view.

@gdjacobs - I did not know that. If I remember correctly, my original CD only supports CM-32L/LAPC but not GM. Good to know.

I remember that Mortal Kombat II for the PC has both MT-32/CM-32L and General Midi (Sound Canvas) soundtracks.

The DOS port of SimCity 2000 had 4 different versions of its MIDI soundtrack, one of which was tailored to the instrument presets of the MT-32. This was 1994.

Paku Paku v1.6 from 2011 supports the MT-32.

Depends on what we mean by "support". Several late 90's games still "supported" the MT-32 via the Miles sound system. Most of them were definitely not optimized for it though, as the Miles audio driver was merely a GM to MT remapping table.