If you had a degree in the field then I would have hoped you could have spotted methodological problems. But I guess not.
Anywho, according to the FBI THEMSELVES for the 2019 UCR, which is the most recent:
Of the 18,667 federal, state, county, city, university and college, and tribal agencies eligible to participate in the UCR Program, 16,554 agencies submitted data in 2019. [1]
Let's run some numbers here... 16554/18667 = 88.6%. This means that, for 2019, the FBI WAS MISSING MORE THAN 1 OUT OF EVERY 10 POLICE DEPARTMENTS.
So, AT BEST, you can claim that we have 88% of all reported police department arrest statistics. However, this would be wrong:
These and additional data are presented in the 2019 edition of the FBI’s annual report Crime in the United States. This publication is a statistical compilation of offense, arrest, and police employee data reported by law enforcement agencies voluntarily participating in the FBI’s Uniform Crime Reporting (UCR) Program. [1]
In other words, the FBI is simply just republishing raw data. There are undoubtedly mistakes in the data. Furthermore, every police department has different classifications for race and, in many cases, race isn't even reported. So for many crimes we have no idea if the race was even properly attributed.
This is what leads them to state:
Caution Against Ranking—Each year when Crime in the United States is published, some entities use the figures to compile rankings of cities and counties. These rough rankings provide no insight into the numerous variables that mold crime in a particular town, city, county, state, tribal area, or region. Consequently, they lead to simplistic and/or incomplete analyses that often create misleading perceptions adversely affecting communities and their residents. Valid assessments are possible only with careful study and analysis of the range of unique conditions affecting each local law enforcement jurisdiction. The data user is, therefore, cautioned against comparing crime data of individual reporting units from cities, metropolitan areas, states, or colleges or universities solely on the basis of their population coverage or student enrollment.
If the people COLLECTING THE DATA say it is not complete enough to infer any real statistics about crime rates, then who are you to suggest any different?