Repairing a e2boot USB key

I’m not sure what you mean by “recreate the USB setup”? If you mean repairing the filesystem, I’d like to but so far I don’t really understand how.

Anyway I tried to install MultibootUSB package (https://github.com/mbusb/multibootusb/releases/download/v9.2.0/multibootusb-9.2.0-1suse.noarch.rpm ) but YaST gives this error message:

Erreur : INVALID :multibootusb-9.2.0-1.noarch (file-ad19f930): Échec de la vérification de la signature [6-Le fichier n’est pas signé]
Header SHA1 digest: OK
MD5 digest: OK
Le paquet n’est pas signé !

(the package isn’t signed)

For an external package it would make sense that the maintainer’s signature is not in my keyring but I can’t see a way to add it in the website’s download instructions?
Or is the problem caused by something else?
Is there a way to install it though?