How to keep PPA's enabled during 18.10 to 19.04 Release Upgrade?

Question

During release upgrades, PPAs and 3rd Party Repositories are disabled:

• What's the best way to re-enable PPAs/repos after an upgrade?

How can disabling of PPAs and 3rd Party Repositories be prevented when upgrading 18.10 to 19.04?

Answer 1

This article:

• Ubuntu Users Can Now Keep PPAs And Third Party Repositories Enabled When Upgrading To A Newer Ubuntu Version

... describes a new ground-breaking development for Ubuntu users:

Brian Murray, Ubuntu Bugmaster, says this should solve many of the issues people are encountering when trying to upgrade from one Ubuntu release to another. I'd also add that his makes it easier to continue receiving updates to software installed from PPA / third-party sources after an Ubuntu upgrade, while also not removing software that might be otherwise removed due to incompatibility when upgrading.

You can use (in 18.10 now, in 18.04 soon) a new flag:

RELEASE_UPGRADER_ALLOW_THIRD_PARTY=1 update-manager -d

Note: Only PPAs supported in the new version will be enabled:

It's worth noting that you may still see a warning about third party sources being disabled on upgrade, but those that support the Ubuntu version to which you're upgrading will not be disabled.