SQL query with "INTO OUTFILE" does not work on MariaDB 10.4 but does on 10.0
Use

SELECT *
FROM ( SELECT 'Name','Address1','Address2', 'City', 'State', 'Zip', 'Phone', 
              'SSN', 'Credit Card', 'County', 'Comment', 'Company'
       UNION ALL       
       SELECT name, address1, address2, city, state, zip, phone, 
              ssn, credit_card, county, comment, company 
       FROM testcust  
       WHERE type = '0'         
     ) subquery
ORDER BY name = 'Name' DESC, name
INTO OUTFILE '/tmp/sellers.csv' 
FIELDS ENCLOSED BY '"' 
TERMINATED BY ',' 
LINES TERMINATED BY '\r\n'
);