The toilet drain pipe is flowing to Nirvana!!

And that wasn’t noticed during installation? - where did the soup go then, backflow of the solid components in the pipe and seepage of the water at the end of the pipe onto the floor slab?

The floor slab/earthworks were carried out by the client, the house was placed on it. The drainage ended somewhere, not particularly deep in the ground in the front yard. You can’t blame the prefabricated house builder for that (unlike the builder of the OP). You have described the result accurately. Backflow and swamp in front of the front door.

A fucking swamp, well then enjoy your meal

No joke? The sh*** is running down your walls?