I have never been to an event with a "side dish" auxiliary category.
But--the organizer sets the rules for all the auxiliary or ancillary categories.
You will need to ask direct questions to the event to get correct answers.
In general, the entries I have seen for "anything but", "desserts", and all of that are works of art!
Looked like the Iron Chefs or some 5-star restaurant chef prepared them.
Tough to get noticed for a basic cook like me
"Flirtin' with Disaster" BBQ Team (RETIRED)
FBA and KCBS Cook and Judge.
Former owner of a WSM, a Smokey Joe, a Charbroil Commercial gasser (junk), the legendary "StudeDera", a FEC100, a Fast Eddy PG500, and Sherman the Wonder Trailer.
Now cooking with a Yoder YS640
Proud Pellet guy cooking on real wood.