I think for DOS you can download this package and just use the 1688 driver in there for the 688.
ESS 1688/1868/1869 Pre-installed for DOS
Actually, the card should work without any driver, except the MPU-401 midi interface. I wonder how the MPU-401 midi interface is supposed to work on this older 688 chipset. Read somewhere it needs a TSR, since it is not MPU-401 compatible in hardware. But if you don't have midi hardware anyways, it does not matter.

For Windows 95: The 688+1688 drivers are already included in Windows.

For Windows 3.1: ESS ISA cards DOS, Win 3.x drivers

Would the 1688 drivers work for 688? Wouldn't the ES688 DOS Install file here be a better idea? http://vogonsdrivers.com/index.php?catid=17&menustate=45,35

Also, I'm completely stuck on configuring the jumpers on this thing. I set the Audio Address to 220, MPU Address to 330, I closed the Joystick enable jumper but got stuck there. There is no IRQ or DMA jumper as far as I can tell. There are only a bunch of CD-ROM jumpers that I am confused about, so some questions:

The CD-ROM controller can be set to SONY, MITSUMI, PANASONIC or NONE. There are SONY, MITSUMI, PANASONUC and IDE connectors on the card. As far as I can tell there is no way to enable or disable the IDE connector, you can only set it PRIMARY or SECONDARY with JP3 - so what I did is close CT0/CT1 and set addressing mode to None and IDE to SECONDARY. I have no idea how this will work with the onboard IDE controller however, as the board already has 2 IDE connectors. Will this override the onboard Secondary IDE? Should I connect my CD-ROM to the Sound Card or directly onto the mainboard? SMH.

Also, there is a big jumper block at the bottom of the board labelled CD-ROM, which can be used to set PRIMARY or SECONDARY, DRQ, DACK and IRQ - are these for vintage pre-IDE CD-ROM drives that require these settings? I set it up as Secondary, DRQ 1, DACK 1, IRQ 11 from vague memories of what they should be. But they won't even be used if I use an IDE CD-ROM and connect it to the mainboard I guess?

That other driver you found; seems like a better match, yes. But it should not matter much.

The jumpers are confusing indeed. I suspect the card is hardcoded to IRQ 7.

What if you boot to DOS, just type 'SET BLASTER=A220 I7 D1 T3', then try a DOS game that is configured for Sound Blaster Pro or ESS Audiodrive?