I am a GNUnet developer. As soon as I get my Librem 5, I will try to get GNUnet running on the Librem 5. After that we have to do optimization regarding battery and bandwith usage, and some general issues (We are doing a basic refactoring of our transport subsystem at the moment.) we need to finish until GNUnet can be used on the Librem 5 and other devices for daily use. This is work not finished in a few month, especially if you consider that not even a full time equivalent developer resource (I am working 50% on GNUnet, and some others even less) is working on all that.
cadet-gtk is a cool application prototype and evolves fast to have decentralized group communication, but also depends on the transport subsystem of GNUnet we are actually working on.
The actual GNunet Debian packages are outdated, but there is a good chance there will be a new Debian package maintainer for GNUnet again!