As a former Debian user, I "kind of" remember that I should only use one of the package managers...
synaptic, but not the three in combination 'cause there may be conflicts, they don't mix well.
I don't know where I have heard it, but it has left its memory print. So I just want to check with you if it is really not advised or if it is an urban legend and it is completely safe. Could you confirm this ?
Is the cleanest way of installing a package is still using the command
checkinstall before invoking