I tried playing the game with the v7 mapgen, and found myself in an infinite desert with no dirt, grass, trees, or any kind of vegetation at all. I'm not sure what version i'm playing, it was installed using the minetest's Content tab (so probably the latest version)
PS: i found out what version i have installed. it's the 0.06 one
I tried to reproduce the problem myself, downloaded the game, created a new world with v7 mapgen (all mapgen options enabled except floatlands), and THOUGHT it hadn't worked (screen was all black), but it turned out I spawned inside a tree trunk. I turned on fly+noclip to get out of it.
So v7 worked for me, but maybe the game should check the player's starting position and ensure it's not inside a solid, or push players out of solids.
What happens if you run the game with a fresh minetest.conf?
iirc, there's currently a bug in the latest version of Minetest where game-specific settings wind up getting propagated to the global config.
Kimapr, your problem is that your minetest configuration has disabled biome generation, I think. That happens after games are installed, occasionally. I would recommend seeing if you can search up mg_flags in your in-menu settings; the biomes flag might be disabled, causing the biome generation to not happen.