With mp3tag how to manage this, please ?

All MY music IS ripped in flac.

When I have in tag artist : David Bowie, how to have in ArtistSort : Bowie, David ?

Many thanks in advance

I am not sure if FLAC knows the ARTISTSORT field.
To fill the field ARTISTSORT with the contents of ARTIST use the converter Tag-Tag for ARTISTSORT and enter %artist% as contents.

Then you have to do the swapping.
Create an action of the type "Replace with regular expression" for ARTISTSORT
Enter as search string:
(.) (.)
Enter as replace string:
$2, $1

Please note that this action may lead to funny results if the artist does not follow the pattern of forename and name.

Great !
Thank you very much