Cut the vegetables into large chunks. Chop the vegetables separately into very small pieces with a food processor.
Combine the chopped vegetables in a very large bowl. Sprinkle with the salt and toss well to combine. Cover and refrigerate for at least 4 hours and up to overnight.
Drain the vegetables in a colander (do not rinse). Make the brine: Combine the vinegar, sugar, ground mustard, mustard seeds, and turmeric in a large nonreactive pot. Bring to a boil. Reduce the heat to low and simmer for 10 minutes.
Add the vegetables to the brine and return to a boil. Reduce the heat to low and simmer, covered, for 10 minutes, stirring occasionally.
Pack the chowchow in hot sterilized glass jars. Wipe the rims and jars and seal with the lids and rings. Process using a canning setup or if planning to store in the refrigerator, let the chowchow come to room temperature before refrigerating.