My father grows sugar beets in Michigan. The hybrid field varieties he grows are nearly indestructible, I've helped through the mechanical harvest. They'll roll off a the top of a pile on a dump truck, off the side, drop 10 feet onto pavement and be no worse. Their size prevents more then one in a standard kitchen pot. They would be hard to process without special equipment.
He has also mentioned the seed thing this year. He says there are 3 big providers. 1 failed for whatever reason, 2nd scrambling to cover increased demand, 3 nobody likes because you don't get enough sugar content in the beets. I assume he uses GMO when he can, but such topics are off limits for the sake of family harmony.
Anyway be great to know what heirloom varieties have worked. Sounds they may be more practical then then the modern monsters. I assume they are both smaller and more tender. The drawback is they will have less sugar content and probably be "beetier."