As I said, the version on Github can't be tested!
It's the only thing I can do (and translate into French, if necessary), I'm not a coder.
Adding an image fails, you created an issue on april 3 and nothing new.
So I think I will look for another gallery extension. My friend is not able to migrate herself and I don't know what will happen to me in a year's time, I'm not young anymore.