Anyquery is a SQL query engine that enables you to execute SQL queries on virtually anything, including JSON files. Moreover, as it can export a query result to a CSV file, you can transform a JSON file into a CSV file with a straightforward SQL query.

anyquery -q "SELECT * FROM read_json('path/to/file.json')" --csv > file.csv

Additionally, you can modify each column using functions such as upper. For example, the following query converts a JSON file to a CSV file and converts the name column to uppercase:

anyquery -q "SELECT upper(name), age FROM read_json('path/to/file.json')" --csv > file.csv

See the functions documentation for more information on the available functions.