Turned out that the trial version of the game, in fact, contained every campaign with their text translated to English. It was only a minor mistake from Sedov to forget about it and not including them in the full version of the game.
So I copied the demo's maps to the full game directory, replacing all of them with the demo maps. I played some of them but could check the texts in the game's map editor as well.
Turned out there's no really consistent story.
The game has five campaigns: 4 played on the Onimod side and one on the Bostvana side.
The Botsvana campaign is not more than a beginner tutorial, with some interesting story elements to wrap around. (find ancient ruins, travel to an island to find a golem, etc)
Onimod campaigns consist of a tutorial, a story of "fighting intergalactic corporations" (which involves Onimod vs. Onimod fights, mostly) and two stories of Onimod-Botsvana conflicts. These are "Masters of Destinies", in which we fight against a pirate clan of Onimods, and "Occupation of Planet", which is quite self-explanatory.
Interesting enough that "Masters of Destinies" contain inter-faction conflicts (Onimod-Onimod, Botsvana-Botsvana), with tribals something even helping the Onimods. It even contains a quite interesting twist, when an Onimod ally turns out to be a pirate, and instead of attacking the real pirate base, he tricks the player to destroy a settlement of the "Space Police".
"Occupation of Planet" ends with Onimod dominion over the tribals but it's not really taken seriously as the amount of texts appearing is quite minimal, it doesn't even provide a proper ending or whatever. Which is sad because even with the lack of a consistent story, this would have been a great finale.
So in general, the game is much different from what I've expected, but I still consider it an original and interesting (yet a bit ugly) piece of gem from the heritage of the 90s.