The societies with the least incels percentage-wise would probably be countries with arranged marriages and the highest level of culturally-promoted/"enforced" monogamy.
Basically the more "conservative" Muslim countries where there isn't that much Western influence yet, particularly the rural parts.
Also rural parts of the third world in general, places with high birth rates.
Countries where a lot of males were killed in wars probably also have very low amount of inceldom.
When it comes to European ethnic groups, I think Albanians probably have the least incels in society, percentage-wise. They seem to be the most clannish and family-oriented out of the European ethnic groups, very nationalistic too and tend to marry within their own ethnic group. Some of them are also strict religious Muslims. I know an Albanian who is a legit 1/10 truecel yet he has family and two kids. Their birth rates are relatively high too, the highest in Europe I think.