While its tribal time was a long time ago, one of the best examples for ethnicity balance would probably be Switzerland which has four different official languages and quite a number of balance ensuring policies, both explicit and implicit. Keeping that in place required a large self-discipline and sometimes harsh decisions, so e.g. when in 1919 the Austrian state of Vorarlberg requested to become a part of Switzerland which would have been culturally fitting, it was rejected. Among the reasons given was that the Schwyzerdütsch (swiss German) speaking part was already in the majority and that accepting another Cantone (Swiss state) would topple the internal balance.
Considering the diverse historical backgrounds, beliefs, cultural norms and values that exist in multiethnic nations, it is not possible to separate tribal sentiments from politics. This strategic exploitation of ethnic divisions is commonly adopted in developing countries where politicians leverage tribal loyalties to mobilize support towards political agendas.