I don't have the card. Never seen a Trio with audio ports either.
Have you tried it out?
Windows 98SE and ME should have the drivers build in, but dunno if the audio part would work in it.

This card looks a lot like yours, except missing audio ports and the lower connector is missing. Odd they mention the memory is not upgradeable while the pic shows 2 empty memory sockets 🤣

the audio connectors get activated when you install the mpeg/video decoding addon board

edit:
here is the card I have - audio connectors are internal on this design - different setup but the same idea I believe

there is some more info here What MPEG daughterboards attach to S3 cards? , I still have no idea how to use the addon card 🤣

Yep its for decoded audio - yours look like passthrough solution similar way how Voodoo 1/2 doin video signal. For sure you need Scenic MX/2 decoder module - http://www.vgamuseum.info/images/doc/s3/poscmx2.pdf and compactible video player + it works only for MPEG-1.

That thing is awsome. The chips looks like the same one used in most mobile / embedded solutions. Great find.

vlask, have you find a compatible video player that works with it?