Everytime I do-release-upgrade it disables my PPA's I need, so I need to re-enable them by checking the box in Software & Updates. A few releases later, I now have a jumble of various channels for these re-enabled PPAs (artful, bionic, cosmic, and even debian ones like jessie etc in /etc/apt/sources.list.d/)
I get no errors or warnings about this. But it feels wrong deep down in my soul. Counsel?
EDIT: I can confirm having a mix does cause odd bugs, it's best to keep them all the same
As you are re-enabling the PPA's, it's a good idea to visit launchpad and see if there are version of the PPA available for the release that you are using.
Using older (newer) PPAs may work, and the system is not going to stop you, but sometimes worse things than "The program won't run" happen.
Please see the pinning page.