I thought, that at the market, because the butchers also deal with "pre-seasoned meats" and such that there are CC issues?
To be a little more specific..... Butchers, for many health reasons, unrelated to gluten CC (sanitary and disease related), practice some of the most diligent processes in cleaning their tables, knives, etc. They mostly don't use butcher block wood anymore as that harbors meat residue and grows bacteria. Instead they mostly use stainless steel tables. Most pre-seasoned meat comes pre-packaged and butchers don't put it on their table - and only supermarket and places like COSTCO's butcher shops would have pre-seasoned meats anyway. Most pre-seasoned meats don't contain gluten either. If you watch them, to avoid cross contamination between different types of meats, they laboriously clean their tables between each cutting - and larger market butchers have multiple tables so that they don't do chicken and beef and pork on the same tables. The slicers are cleaned frequently as are the hamburger grinders.
I still say that getting meat directly from a butcher shop is probably the safest place to get meat. And liver doesn't require much butcher preparations to sell either. The most important thing about liver is that is is very fresh and kept cold.