Problem with saving under eps format

Hello. I have problems with saving my matplotlib figures under the eps format.

I updated my python/matplotlib to 3.9.2/3.5.1. Since then I do not manage to save figures under the eps format (png or pdf work fine though). The saving process goes fine but I get a transparent eps file (that opens well). Please see below a minimal working example,as well as the output.
Many thanks for your help.

import matplotlib.pyplot as plt


plt.savefig("test.pdf") #fine if extension is png or pdf for exemple #no pb with display

PS: another perhaps useful info is that the update in python/matplotlib came with an update of my Debian from 10 to 11. So many things change at the same time. I investigated imagemagick but it looks fine with old eps files.