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Here is the rest of what Dave from Appleton WI told me:

He noted that because of the rib rub, all ribs, tips, etc EXCEPT the
baby back ribs will contain gluten.  The baby back ribs would need to be
ordered without the sweet and zesty sauce.  He said to order "baby back
ribs naked".  Then, the other sauces are at the table and you could use
texas pit sauce or the Georgia mustard sauce.  The Rotisserie chicken is
fine.    He stated that the coleslaw and potato salad are GF but the
fries are not cooked in a dedicated fryer at most locations and the pork
in the pork and beans contains gluten.  He was extremely helpful and
also stated that if you called ahead, some of the restaurants would
smoke a slab of regular (not baby back) ribs for you without the rib
rub, making them GF.  However, this process takes 4 hours so you need to
plan.