For a container, these lids https://www.amazon.com/Maintenance-silicone-waterless-fermen... on mason jars make me glad to be alive just after their invention, given that people have fermented food for millennia.

Dead simple, no mold, no burping necessary. Chop vegetables, add salt, mix and mash, put in jar with one of these lids on top. The next morning you'll see it bulging, letting the CO2 out but no O2 in.