Here is an updated error message list from lunar:

# journalctl | grep Extension
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
Jun 28 08:27:35 vougeot gnome-shell[4088]: Extension <email address hidden> already installed in /<email address hidden>. /<email address hidden> will not be loaded
[...]