PPAs are fundamentally flawed. Since each repository is separate, they only care to maintain consistency internally, plus the packages of the Ubuntu version they were based on.
Adding a PPA and using its packages on your system takes your dependency tree into a “cul de sac” where only that PPA is reliable.
But of course people use multiple PPAs so what happens is that the dependency tree grows increasingly unrecoverable.
Eventually you get the dreaded “requires X but cannot be installed” errors which pretty much mean you’ve hit a dead end. You can recover your system from it (aptitude can provide solutions) but they are extremely invasive, basically come down to uninstalling and reinstalling thousands of packages to bring your tree back to a manageable state.