What's the story?
I would like to gather all of the story-related information together in one place. Since Mechaenetia is at its core a game of the sandbox/survival genres, the story that ships with the base game doesn't really compare with most games. There doesn't necessarily have to be a story at all.
Nevertheless, let's consider the stories in other games that I think might be similar to Mechaenetia. These are all survival games and most of them are also sandbox games.
Factorio (real-time strategy/construction and management simulation/survival)
The player character is an engineer who has been shipwrecked on an alien planet. While fighting off hostile creatures, the player must harvest resources and set up a factory in order to construct a space ship and escape.
Minecraft has no backstory, but it does have an ending. The closest thing to a story would be the optional in-game objectives ("Advancements", formerly "Achievements") which guide players to defeat the final boss, the Enderdragon. After defeating the boss a portal appears. Stepping through the portal will show a long fourth-wall-breaking poem about life and the universe, then roll credits.
No Man's Sky (action-adventure/sandbox/survival)
The player character is presented as a retrograde amnesiac who feels compelled to travel to the center of the galaxy. The (mostly optional) story is the player's journey there, and the backstory is revealed by the end. I believe there's actually two branches to the main story now.
The player character is a newly graduated Protector, but at the graduation ceremony a planet-destroying monster consumes Earth, homeworld of the Protectorate. The player escapes in a spaceship, and later becomes stranded in orbit of an alien planet. The game proper begins as the player beams down to obtain fuel for his or her spaceship. Starbound features both a formal linear story and random missions.
Wurm Online (massively multiplayer online roleplaying game/sandbox/survival)
The player's backstory is given when first starting the game: you step through a one-way portal and arrive in the strange and fantastical world of Wurm. Wurm itself has a backstory involving kingdoms and wars and religions. Because the game is both an MMORPG and a sandbox game, each server has its own lore based on player actions within that server.
At present, the only thing I could find that touches on a potential story is one post in the worldbuilding topic,
I believe this “players all know that they are players” means the player has no backstory. It is not clear whether or not the base game will tout a main story arc.