The Agat-9 is one of my white whales - it's not particularly Apple II compatible (the graphics are quite different, actually) but the documentation is entirely in Russian and Google Translate can be weird about it. (Example: this page when translated in Chrome it changes the Cyrillic characters to their Latin equivalents but doesn't actually translate).

The page for the card itself translated OK and it's a fairly standard design except for the noise channels. 2 8253 PIT clones driving DACs for the tone channels is the sort of thing we've definitely seen before.