Idk about for Europe. But you might have luck with Grindr if it’s available in your country. It tends to have a younger crowd. Though most your sites/apps are heavily flooded with bottoms so it’s difficult sometimes to get the attention of a guy you’re interested in. Adam4adam seems to be an older crowd. Their interface is kind of archaic. Swinglifestyle is primarily marketed towards swinger couples but there are some bi dudes on there. I think you HAVE to pay for an account there now though.
There’s not really anything specific to bi bbc bulls though. That would be a niche platform which usually don’t last long. Your bigger ones survive because they’re more inclusive.
Sorry I couldn’t just give you a url for a site that fits exactly what you want but I think you’re gonna have to cast a wide net and try to pick the “fish” you want to keep.