Thanks a lot for the hint! The driver works perfectly - only, I take it, one needs to self sign it for Windows to not fail loading it when not in a special boot mode. Oh well, no rest for the wicked, I guess...

E: For DOS enabling legacy FM, and disabling OPL port forwading got music in Gods and Magic Pockets back with VSBCMI (and I checked Wolf3D as well). VSBCMI, by the way, does not attempt to detect if the chip supports OPL3 emulation, instead it simply has a command line argument to enable the corresponding bit. Will be studying this further to find a rational way forward with this.

E-E: More "problems" have been cropping up with the rev.37 card. It appears, it was running at 48k when configured for TOSLINK output, and MIDI UART is very picky and requires additional delays around port reads and writes, which were not required for the "6ch" chip. In legacy UART emulation mode the chip works just fine, and I was also seeing if this could be taken advantage of, but sadly could not get VSBHDA code to not interfere with legacy UART even if it was not virtualizing port 330. I think version 1.7.2 of VSBCMI is finally taking shape, and since someone has kindly shared pdf of the card's manual which explains how S/PDIF input/output is configured, I might try and see if digital CD input works after all...

VSBCMI on github is updated with 1.7.2 binary, guide updated as well.

The TSR works okayish with a Winfast 4X. Some observations made during testing:
- Cyril Cyberpunk surprisingly does not predictably hang the system on quit
- Malcolm's Revenge and Hand of Fate CD are not entirely stable (these and the above seem to be speed sensitive, as well as the above)
- Archimedean Dynasty hangs at startup, even though it works with SBEMU
- Tartar (Doom source port for DOS) started crashing when lots of stuff gets preloaded; no idea at this stage if this is sound related

Digital CD-in did not work for me after all, but oh well...

E: A small update.

- Archimedean Dynasty does not like JEMMEX VCPI, so sending NOVCPI to JEMMEX before starting it actually gets it working with sound; it crashes loudly upon exit unfortunatelly. Turns out it uses Causeway DOS Extender by default, but there are also executables ending with ...D4G and these use DOS4GW, which is pretty much compatible with VSBCMI/VSBHDA, so problem solved
- Tartar seems to hate either screen font or keyboard driver my FreeDOS had installed, and without that loaded just fine, with sound. I made some adjustments to MIDI UART delays in VSBCMI however, as values in current published build made playing with MIDI music feel somewhat choppy (compared to OPL3), and now problem seems to be solved as well
- Unrelated to the sound topic, I noticed stability issues with games using mouse, no matter which CTMOUSE version I use, since I switched from an AT/2 to a USB mouse. I now attribute some instability in Tartar and certain Westwood games to this, and not sound drivers
E-E: and couple more remarks on compatibility:
- Inherit the Earth is a DOS16M game, so no surprise it misbehaves
- Whizz does not seem to start at all in FreeDOS, regardless of TSRs or memory managers; it starts in MSDOS but crashes when sound gets initialized

Additionally I tinkered a bit with SBEMU and this WinFast 4X card I have and neither prebuilt, nor locally built versions (1b4, 1.1, 1b5 nor trunk) work with it, crashing one way or another, or producing no sound.

v1.7.3 ships 16-bit version of VSBCMI in addition to 32-bit one and makes MPU-401 operation for older chips a little bit faster.
I have updated posts above with, e.g., addition of Tyrian 2000 to the list of games, and am also putting a list of games into the new howto added to VSBCMI source code.

v1.7.4 is out; this one is built with OpenWatcom for both 32-bit and 16-bit versions and includes some bugfixes from VSBHDA 1.8.
X-Wing and Monkey Island now work (require /CF1 option), and Black Zone works as well, but with software OPL emulation enabled (/OPL1 /CF1).
Updated the compatibility post above, as well as the HOWTO found with VSBCMI source code.

E: All of a sudden v1.7.5 is around the corner with a small, but important tweak that got the chip's own FM in Black Zone working, and I hope will help with some other games. Instead of forwarding to card's PCI FM ports, /DF10 now sends directly to 0x388 in cases when software emulation is off (/OPL0) and chip's own legacy FM is not disabled (default).