Okay, some really bad news but also a suggestion for a way forward.

The Guppe groups domain name was sold by their registrar before they could renew it. This means all Guppe groups are broken, and their web addresses point to a spam blog

However, there is another group provider called FediGroups, you can find out more on their site:

️ https://about.fedigroups.social/home

FediGroups has features that Guppe never had, including private groups.

(More info about #Guppe situation: https://github.com/immers-space/guppe/issues/118 )