Stop treating it like it's an epidemic. Those people are few and far between.
They completely assimilate into the local White culture. And tend to be alright people. One gets the sense that they seek to connect with their Somali side while not outwardly stating it as such. It's awkward when they do the ethnicity reveal, and all you can do is treat them like you're white friends.
There is this chick that I got to know through an cadaan friend who revealed she was Somali, and I had tried to avoid that as I knew she looked Somali mixed, not going to lie. So when she said it and looked at me like a child that wanted validation, all I could muster was a, "Oh, that's .. that's cool." Reflecting on it now, I think I was too underwhelming, but I thought it was too awkward since she was no different than White people in behavior and everything. I could not start changing tones because that would be as if I were a foreigner to her. I was not keen on maneuvering her complex identity issue. She was very beautiful and too into me. Her half-Somali side was an elephant in the room that I wanted to avoid because she clearly expected me to be a source of identity recognition or something. So, I treated her like the average white woman.
Deadass, I think she wanted me to be a proxy daddy for her aabo who left her. That's too much for me because I was not the most culturally enriched Somali. I grew up in a culturally mixed environment myself.