First, forget about ESS - they do claim "Supports Microsoft® WindowsTM Sound System®", but it's about WSS software, not about compatibility with WSS card.

Second, I'm not aware of any card with 100% compatibility with WSS card.

WSS card is not just AD1848 codec + OPL3 synth.
It's also status/config registers, by default at 530h..533h - I think they are handled by one of the minor chips.

Non-Microsoft cards may be fully compatible with AD1848 and OPL3, but need custom software for configuration/initialization - WSS drivers alone aren't enough.

It seems that GUS daughterboard by @Tiido has an option to work with WSS drivers alone - but it's not a normal card:
Re: SB compatibility daughterboard for GUS Classic

I've had good experiences with WSS compatibility on my OPTi 82C930 card, but that was while playing DOS games which support WSS for 16-bit audio. It even worked fine with more problematic titles like Tyrian.

Never tried that card under WinNT 4.0, but I remember that its Win9x drivers were kinda crappy. It worked well enough under Win 3.1 though.

I'm afraid Opti chips need SNDINIT or UNISOUND to set them to WSS mode.

All of the Crystal and Yamaha based ISA sound cards I've tried have had good WSS support. Some games will fail to auto detect them and some are fussy about resources, but most work with some messing around.

The main thing is that while a lot of cards are WSS compatible on the way sound is played and recorded, they are not at all compatible on the resource assignment method. On most cards those registers are read only and reflect partial state of the actual resource configuration which is done in some other method. For example WSS conf register does not support IRQs 3 or 5, only 7, 9, 10 and 11.

FWIW, I have found additional Alpha NT drivers for:

* Ensoniq AudioPCI, which is also everywhere.
* LynxONE - seems to be some kind of pro audio production card. Actually looks pretty capable, though that breakout cable is eye watering.
* Turtle Beach Multisound and variants - these seem to come from Sonic Foundry. Seems Alpha NT got some DAW software like Acid/Sound Forge. Makes sense - if your Windows DAW software hit x86 single threaded performance, porting to Alpha was the only way to make it faster without also porting to Unix.

It doesn't help much for VMS/Tru64 though, which is why I wanted something that does WSS without ceremony.

Ideally, you want 3X-AVH10-AA, the Ensoniq AudioPCI based card Compaq sold for AlphaStations.

I just actually found out about that card. It looks like a normal ES1370 card based on the blurry bigfoot pictures from resellers, so I got one of those. Unfortunately, the NT drivers BSoD (tried both 4.0.16 from the AudioPCI CD and 4.0.23 from the alphant FTP); have not yet tried VMS or Tru64 yet. Might need to reinstall NT since I used the EB164 HAL instead of the PC164 HAL, which might have something to do with it. I think I might have also picked the wrong card though; I should have got a ES1371 at least for OpenVMS based on these PCI IDs. (CT5880 might also work based on that...)

I also found out there are ESS AudioDrive drivers; the zip file name to look for is "ess40.zip" from the softpaq/alphant directory of the compaq/hp FTP. Don't have one, but good to know it might be back in contention.