After a lot of datasheet digging, some programming experiments I finally got sound working !
The problem turned out to be limited range of IO given to the ISA side. There's 16 address mapping registers, half of them were ISA related but some were bogus stuff and just few things that only were done for onboard things... I have no idea how the thing was even supposed to be usable with expansion devices out of box...
In any case I made an util that gives $0400 to $0BFF range to ISA. $0000 to $03FF already was given which was enough for some stuff.
DMA channel 0 seems to be non functional though, and that was main reason other simpler cards like SB16 didn't want to play along.

The device is disappointing though. It has a 133MHz CPU, but it is a 486 class chip rather than Pentium class, which means it fair bit slower, well under 100MIPS. The IDE controller is PIO only which means any significant HDD access eats up too much CPU and there will be a hiccup, video also sits on ISA and needs lot of CPU power to update. Since there is only 32MB RAM it means you need swapfile and that means extra HDD access which also means more hiccups.
Good thing is that the integrated LAN chip sits on PCI bus, and experiments with network and internet streaming are positive. LAN access is much faster than HDD access here, so it eliminates one bottleneck right away. I can stream WAVs from LAN but not from HDD for example.

The next plan is to overclock the thing, replacing that 33MHz oscillator with something faster :P
I'll also see about tweaking the ISA bus speed, it can go up to 33MHz here, I don't expect the devices to keep up with anything much beyond 10MHz... but all gains matter here. Squeezing extra blood out the stone lolololololol

In any case I am incredibly happy I finally have sound :D
*continues to listen italo.nu*