Hi

I am on Ubuntu 16.04.
When running 
sudo apt-get upgrade I obtain 

The following packages will be upgraded:
  akregator-trinity amarok-common

Etc all together some 66 packages 

Then saying yes 
WARNING: The following packages cannot be authenticated!

Then even saying yes I obtain 

Err:11 http://mirror.ppa.trinitydesktop.org/trinity/deb/trinity-sb xenial/main-r14 amd64 kate-trinity amd64 4:14.0.10~pre13-0ubuntu16.04.0+1
  404  Not Found

Can somebody please tell me what is wrong here?

Thanks and regards

Uwe Brauer