Here's a SoundFont that the FM fans here will love. It is based on the online libre chiptune synth program JummBox, which has canonical GM patches defined by the author based on SGM (the patches however are synthetic and draw inspiration from certain chiptune phenomena too), but the program didn't have anywhere near a GM drumkit, so I used various libre FM SoundFonts to build one which sounds good and is VERY compatible.

Honestly the bank sounds like a souped-up OPL3. It works even on Fluidsynth 1.x or other players that cap at 1GiB (the SF2 spec and Audigy, Audigy 2, and X-Fi cards can handle up to 4GiB). In 7Zip the bank is only 198MiB, so have no fear of download time. The archive can fit on a Zip 250, LS-240, or Mini-CD. The bank is FULLY compatible with OpenMPT, including the stereo, and each patch is one voice, so the polyphony lines up EXACTLY with how many notes are playing. The samples are NOT muddy like those 32kHz SF2s or such one often finds.

This SF2 works with GM and a bit above, and I've found that MT32 MIDIs can survive best if played in chiptune soundfonts, at least in my experience.

The JummBox bank is available for free at:
https://stgiga.itch.io/jummboxsoundfont
or
https://musical-artifacts.com/artifacts/2722

It is COMPLETELY libre.

I hope you enjoy this!