Ubuntu – Comparison of dpkg/APT/aptitude/Ubuntu software centre/synaptic package manager

For what I know, different package managers can have different opinions about which packages are installed automatically, or at least it was true time ago, not sure if it is yet so.

This can have consequences on autoremove subcommand (be aware that aptitude does not have an autoremove subcommand, but executes autoremove automatically).

So one can have unuseful packages hanging around, not a big problem anyway.

Also, they can have different opinion about which packages are blocked, but this should not be an issue for the normal user that often make no use of this feature.

The dependencies and conflicts resolution algorithms are more or less equivalent, so in conclusion I think the user can mix the use of different package manager without the fear of breaking something.

You'll have to eliminate gimp-paint-studio , gimp-gmic , and gimp-plugin-registryto fix your last issue.

sudo apt-get remove gimp-paint-studio gimp-gmic gimp-plugin-registry

For repository , use apt-add-repository -r ppa:user/repository to remove one