It’s really a kitchen sink soup, you can definitely use a pork stock, add bones, bacon, cabbage , and sauerkraut. Very flexible.
beets and cabbage can go into the same borscht, definitely.
some recipes above call for both.
My typical borscht is beet based, without cabbage, but you definitely can add cabbage.
Usually, what’s called cabbage borscht, found at Jewish delis, without any beets, is closer to a Russian and Ukrainian Shchi ( Sweet and Sour Cabbage Soup. ) That’s the cabbage soup I usually make. There was a long thread on Chowhound about that. I’ve been making it for 20 years.
