[Spot] Issue with Debian package signature

Hi all, I am trying to install spot on Ubuntu 20.04 following instructions from: https://spot.lrde.epita.fr/install.html But apt update complains about the signature: W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://www.lrde.epita.fr/repo/debian stable/ InRelease: The following signatures were invalid: EXPKEYSIG 03D99E7444F2A84A LRDE Repository <admin(a)lrde.epita.fr> W: Failed to fetch http://www.lrde.epita.fr/repo/debian/stable/InRelease  The following signatures were invalid: EXPKEYSIG 03D99E7444F2A84A LRDE Repository <admin(a)lrde.epita.fr> Could the signature be expired? I can actually install spot from source but Debian packages are useful for preparing artifact submissions. Thanks, Ocan