I have the following release: https://musicbrainz.org/release/8e6186b2-a407-40cf-9c09-42b4d557b02f/cover-art

Load it with the CAA provider, save it, you now have

▕ rw-rr-▏< sec │ 20K│folder.gif
▕ rw-rr-▏< sec │ 14K│front.gif

Remove it from Picard, disable the CAA provider and enable the Local Files one, add "front" to the regular expression of the Local FIles provider, load the release, save it. You now have

▕ rw-rr-▏< sec │ 14K│folder.gif
▕ rw-rr-▏< sec │ 20K│folder (1).gif
▕ rw-rr-▏53 sec │ 14K│front.gif

↪ md5sum *gif
e0a34d99d3b072e59b1218a58759e541 folder (1).gif
72f2cbb78380cb81508eb35d714bb1f7 folder.gif
72f2cbb78380cb81508eb35d714bb1f7 front.gif