Most Farmina foods are based on chicken or lamb. They have one food that's venison-based:
However, there are no bison/beef options from them.
You might have to look at an RX allergy food made from hydrolyzed protein. It's processed so that the protein molecules in it don't trigger food allergies. Royal Canin makes one that should be easy to get in Europe (Royal Canine Hypoallergenic) but it costs about US$50 for a very small bag, so you may find home cooking or raw is not more expensive than feeding that, and you'll likely bet far better ingredients into the dog.
Many dogs that can handle Bison can also handle Beef, which would be a lot easier/cheaper to get in Europe than Bison. Boar is available in Europe to some extent, but it's not supposed to be eaten -- at least in Northern and Central Europe, it's still contaminated with radiation from Chernobyl's fallout after all these years. Apparently, they're eating forest mushrooms and such that are still sucking up the radiation in the soil. I would be VERY cautious about sourcing boar in Europe for that reason -- or using dog food with boar!
Since you've tried a massive amount of proteins in KIBBLE, I think you might want to consider whether KIBBLE is actually the problem, not all those different proteins. I have an allergy dog who can eat raw beef just fine -- along with many vegetables, including sweet potatoes. But if he eats a limited ingredient kibble with beef and sweet potatoes, he's back to having bloody diarrhea. We figured out during our year of food misery that it was something in kibble that was the difference -- we don't know if it's a binder, a product of high heat processing, or something else, but he's not the only dog I know that has the issue. The owner of a local natural pet supply store has a Great Dane with the same issue -- she has access to ANY kibble under the sun, but after lots of trial and error, she had to put him on a natural diet to save his life.
We transitioned to raw using a base mix (the Honest Kitchen's Preference) which was absolutely FANTASTIC at soothing his GI system. When you add meat to it, it creates a complete, balanced meal. (It has more peas than I'd like, so I'd consider supplementing with taurine until the FDA figures out what's going on with that ingredient.) Adding 6-hour bovine colostrum (a human supplement available at health stores or online) and a probiotic would also be a good idea for a dog with an angry GI system from food allergies.
Another beef option to try would be Ziwi Peak's dehydrated food, out of New Zealand. It's expensive, but it's convenient, high quality, and minimally processed.