I know there is another topic about PCI sound cards in Windows 3.11 - but the initial discussion is rather discouraging...

Well, good news: I just tested today an Ensoniq PCI Audio 3000 and it does work under Windows 3.11, on a Ryzen 3900x system and using an Asmedia 1083 PCI-E to PCI bridge. Also it works on a Haswell machine - Asus H81M-C/i5-4570 which uses the same bridge type. Other PCI sound cards that work under 3.1 (and tested by me) are ALS4000 and Aureal 8820 but they do not work in newer motherboards.

Audio PCI 3000 uses the Ensoniq ES1370 chip which can work with later Creative 137x drivers in Windows 9x/2000/XP - BUT - Ensoniq Windows 3.11 drivers won't recognize Creative 137x chips in any way. I tried like five different Creative cards and all failed detection during the installation. The driver won't work even if is installed manually. (for these Creative cards there is a 3rd party driver, but without MIDI support)

So, the idea is to stick only with original Ensoniq cards in Windows 3.1. (mostly made in 1996/1997)

Also, using the whole driver package you get good MIDI support under Windows 3.11 - I could use Midisoft software in real time, something that I really wanted under Windows 3.11. The MIDI implementation is not bad either for my ears.