As I posted on http://thinkinginsoftware.blogspot.com/2017/12/correctly-generate-csv-that-excel-can.html:
Tell the software developer in charge of generating the CSV to correct it. As a quick workaround you can use gsed to insert the UTF-8 BOM at the beginning of the string:
gsed -i '1s/^\(\xef\xbb\xbf\)\?/\xef\xbb\xbf/' file.csv
This command inserts the UTF-4 BOM if not present. Therefore it is an idempotent command. Now you should be able to double click the file and open it in Excel.
