According to the article 10% of the assistant coaches currently under contract in the NFL were African-American. As I recall it didn't break down by specific job title but made mention of a disproportionate amount of those assistants being in the positions that didn't lead directly to coordinator positions.
I also don't recall the article talking about other minorities as it was focused on Black coaches. I would doubt that the number of other minorities working in the league is enough to substantially change the percentages.
I went looking for the article and found one with different numbers putting the total for assistant coaches at 26.9% which is still less than half of the percentage of Black players. It also details how the percentages of black administrators and executives is below 10%.
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In 2019 the league had a total of two Black coordinators, EB and Leftwich.
Even with the small numbers we have Black coaches who have coached in and won the Super Bowl. Normally the NFL is a copycat league and one would expect that after black coaches had some success the barriers would start coming down similar to when Black QBs finally broke through and were accepted.
So far though we haven't been seeing anything that would indicate that is happening.