I did the opposite direction some time ago and it is possible to manipulate the library.db file using sqlite. The following command should work:
sqlite3 “library.db UPDATE film_rolls SET folder = replace( folder, ‘/home/old_username/Pictures’,’/Users/new_username/Pictures’ ) WHERE folder LIKE ‘/home/username/Pictures/%’;”
I always start DT with a custom --configdir, so it was easy to copy the db folder to the linux installation. However, at the end I decided to start over with a clean config anyway, because Lua was not working, and thumbnails needed to be recreated anyway. So going with a clean config was just faster, when all files have a recent xmp sidecar. But maybe it works for you.
It might be, that I found the sqlite command somewhere in this forum, but I cannot remember …