Description of problem: the sum of listed installed and available packages numbers does not match the value as output for all packages.
Version-Release number of component: dnf.noarch 2.7.5-12.fc28 @updates-testing
Steps to Reproduce in terminal:
1. $ dnf list all | wc -l
2. $ dnf list installed | wc -l
3. $ dnf list available | wc -l
Actual results: Assume outputs resulting from commands illustrated in steps 1., 2., 3, are respectively represented by x, y, z. Currently x > y + z; non-equality would suggest that x might take in account duplicates. Since it's not the case I suspect an issue.
Expected results: x = y + z; Requirement in order for each one to be reliable.
$ dnf check --duplicates (No output). Confirmation by running:
# dnf remove --duplicates
Error: No duplicated packages found for removal.
Some modules are disabled and possibly without default stream, which results into packages not being available. That's why 'all != installed + available'.
These are aspects that could not have been guessed. Now I know.