I think Mokaev is marketed as British but I've seen I think around a month ago on social media he was asking to give him British citizenship. Tsarukyan said that it was idea of UFC to market him as Armenian (he was born in Georgia and lives in Russia; I never seen any info about him holding Armenian citizenship).Oh, I know it's a marketing thing. They're Hawaiian.
Also I've seen info about Polish Chechens that fights in KSW and Polish promotions that they are not fighting abroad because they wait for Polish citizenship while living there as a refugees, I guess (and I am pretty sure promotions put them on posters with flag of Poland).
Brave CF market Eldarov as Bahraini but he said that he doesn't have citizenship and even his friendship with Sheikh didn't help. Kharkhachaev said that he too doesn't have citizenship of Bahrain (and I suspect all of Dagestani who represented Bahrain in amateur mma is still citizens of Russia and none of them are citizens of Bahrain).
I've seen Open FC in Russia was doing posters with fighters and multiple flags (it was mostly guys with Armenian and Russian flags and also Tajikistan and Russia) but I don't know if this pictures really showed which citizenships fighters hold or more like showing connection with their ancestry.