12 bits is not enough resolution. That’s 4096 values. That’s fine if you want to measure temperature to 0.5 of a degree Celsius from 0 to 500.
But we want to measure 1/10th of a gram from -5kg to +5kg. That takes at least 17bits. And that’s if the matching of the load cell to the range of the sensor is perfect. In the real world you probably need to throw away half that, so 18bits minimum.
Realistically you could only get +2kg to -2kg in 1g increments. The noise would likely be on the order of 10 to 20g. And again that’s if your load cell is perfectly matched to the voltage range that the Pi expects to see.
(Alternately you could do ±200g in 0.1g increments to enable probing. But I’m not sure how you are going to have a 200g load cell that survives 5kg extrusion forces, or laying down a kg of filament if it’s in the bed. We are kind of stuck using larger load cells due to the physical system)